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  • How to make a link button visible after another button has been clicked in asp.net(vb) in button_c

    - by Parth
    How to make a link button visible after another button has been clicked in asp.net(vb) in button_click() it says error as "Object reference not set to an instance of an object." i've done this in my code Protected Sub InsertButton_Click(ByVal sender As Object, ByVal e As System.EventArgs) Dim receipt As LinkButton = FormView1.FindControl("LinkButton1") ' receipt.Enabled = "true" ' receipt.EnableTheming = "true" ' receipt.EnableViewState = "true" receipt.Visible = "true" End Sub

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  • How to configure a URL with 3 levels in ASP.NET MVC?

    - by MCardinale
    Using ASP.NET MVC, I need to configure my URLs like this: www.foo.com/company : render View Company www.foo.com/company/about : render View Company www.foo.com/company/about/mission : render View Mission If "company" is my controller and "about" is my action, what should be "mission"? For every "folder" (company, about and mission) I have to render a different View. Anyone knows how can I do that? Thanks!

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  • How can I locate .NET Library property/function that return a particular type?

    - by Michael Bray
    Occasionally I will know that there is a .NET Framework function that returns a particular type of object, but I can't recall the property or function name. It would be really nice to be able to somehow scan the Framework or other DLL for functions that return a particular type of object. (For example, it would have helped when I asked this question, and I have a similar question again.) Can anyone suggest how I might do this?

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  • Ado.net Fill method not throwing error on running a Stored Procedure that does not exist.

    - by Mike
    I am using a combination of the Enterprise library and the original Fill method of ADO. This is because I need to open and close the command connection myself as I am capture the event Info Message Here is my code so far // Set Up Command SqlDatabase db = new SqlDatabase(ConfigurationManager.ConnectionStrings[ConnectionName].ConnectionString); SqlCommand command = db.GetStoredProcCommand(StoredProcName) as SqlCommand; command.Connection = db.CreateConnection() as SqlConnection; // Set Up Events for Logging command.StatementCompleted += new StatementCompletedEventHandler(command_StatementCompleted); command.Connection.FireInfoMessageEventOnUserErrors = true; command.Connection.InfoMessage += new SqlInfoMessageEventHandler(Connection_InfoMessage); // Add Parameters foreach (Parameter parameter in Parameters) { db.AddInParameter(command, parameter.Name, (System.Data.DbType)Enum.Parse(typeof(System.Data.DbType), parameter.Type), parameter.Value); } // Use the Old Style fill to keep the connection Open througout the population // and manage the Statement Complete and InfoMessage events SqlDataAdapter da = new SqlDataAdapter(command); DataSet ds = new DataSet(); // Open Connection command.Connection.Open(); // Populate da.Fill(ds); // Dispose of the adapter if (da != null) { da.Dispose(); } // If you do not explicitly close the connection here, it will leak! if (command.Connection.State == ConnectionState.Open) { command.Connection.Close(); } ... Now if I pass into the variable StoredProcName = "ThisProcDoesNotExists" And run this peice of code. The CreateCommand nor da.Fill through an error message. Why is this. The only way I can tell it did not run was that it returns a dataset with 0 tables in it. But when investigating the error it is not appearant that the procedure does not exist. EDIT Upon further investigation command.Connection.FireInfoMessageEventOnUserErrors = true; is causeing the error to be surpressed into the InfoMessage Event From BOL When you set FireInfoMessageEventOnUserErrors to true, errors that were previously treated as exceptions are now handled as InfoMessage events. All events fire immediately and are handled by the event handler. If is FireInfoMessageEventOnUserErrors is set to false, then InfoMessage events are handled at the end of the procedure. What I want is each print statement from Sql to create a new log record. Setting this property to false combines it as one big string. So if I leave the property set to true, now the question is can I discern a print message from an Error ANOTHER EDIT So now I have the code so that the flag is set to true and checking the error number in the method void Connection_InfoMessage(object sender, SqlInfoMessageEventArgs e) { // These are not really errors unless the Number >0 // if Number = 0 that is a print message foreach (SqlError sql in e.Errors) { if (sql.Number == 0) { Logger.WriteInfo("Sql Message",sql.Message); } else { // Whatever this was it was an error throw new DataException(String.Format("Message={0},Line={1},Number={2},State{3}", sql.Message, sql.LineNumber, sql.Number, sql.State)); } } } The issue now that when I throw the error it does not bubble up to the statement that made the call or even the error handler that is above that. It just bombs out on that line The populate looks like // Populate try { da.Fill(ds); } catch (Exception e) { throw new Exception(e.Message, e); } Now even though I see the calling codes and methods still in the Call Stack, this exception does not seem to bubble up?

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  • Weird behavior when debugging ASP.NET Web application: cookie expires (1/1/0001 12:00AM) by itself on next breakpoint hit.

    - by evovision
    I'm working on ajaxified (Telerik AJAX Manager) ASP.NET application using Visual Studio 2010 (runs with admin privileges) and IIS 7.5. Basically, everything on the page is inside update panels. As for cookies I have custom encrypted "settings" cookie which is added to Response if it's not there on session start. Application runs smoothly, problem was arising when I started the debugging it: Actions:  no breakpoints set, F5 - application has started in debug mode, browser window loaded. I login to site, click on controls, all is fine. Next I set *any* breakpoint somewhere in code, break on it then let it continue running, but once I break again (immediately after first break) and check cookie: it has expired date 1/1/0001 12:00AM and no data in value property. I was storing current language there, which was used inside Page's InitializeCulture event and obviously exception was being raised. I spent several hours trying deleting browser cache, temporary ASP.NET files etc, nothing seemed to work. Same application has been tested on exactly same environment on another PC and no problems with debugging there. After all I've found the solution: visual studio generates for every solution additional .suo file where additional settings are stored, like UI state, breakpoints info, etc, so I deleted it and loaded project again, tried debugging - everything is ok now.

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  • Any alternative to hide querystring from Html.actionlink on ASP.NET MVC Page?

    - by Madhavi
    Hi I have a page called SearchDcouments.aspx that displays all the matching documents as Hyperlinks in the table format as below. When the User clicks on any particular document, the sample url will be: http://localhost:52483/Home/ShowDocument?docID=280 So that the DocumentID is passed as Querystring to the ControllerMethod ShowDocument and the ID is visible in the URL. Now for Security purposes, I want to hide this way of passing the Querystring parameters. Wondering what are the alternatives to hide the DocID from the URL? Appreciate your responses. Thanks Code in the View: <tbody> <% foreach (var item in Model){ %> <tr> <% string actionTitle = item.DocumentType.ToLower() == "letter" ? "Request References" : "Request Slides"; %> <td> <%= Html.ActionLink(actionTitle, MVC.Home.ShowDocument(item.DocumentID))%> </td> </tr> <% } %> </tbody> Code in the Controller: [Authorize] [HttpGet] public virtual ActionResult ShowDocument(int docID) { Document document = miEntity.GetDocumentByID(docID); switch (document.DocType.ToLower()) { case "slide": SlideRequestViewModel slide = new SlideRequestViewModel(docID); return View(MVC.Home.Views.ShowSlideRequest, slide); case "letter": RefRequestViewModel rrq = new RefRequestViewModel(docID); return DoShowRefRequest(rrq); default: break; } // Here - let's get back home return RedirectToAction(MVC.Home.Default()); }

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  • ASP.NET - I am generating an .XLS file with a DLL, how do I grant permissions for writing to file? (

    - by hamlin11
    I'm generating an .XLS file with a DLL (Excel Library http://code.google.com/p/excellibrary/) I've added this DLL as a reference to my project. The code to save the .XLS to disk is running, but it's encountering a permissions issue. I've attempted to set full access for IUSRS, Network Service, and Everyone just to see if I could get it working, and none of these seems to make a difference. Here's where I'm trying to write the file: c:/temp/test1.xls Here's the error: [SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed.] System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) +0 System.Security.CodeAccessPermission.Demand() +54 System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy) +2103 System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy) +138 System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share) +89 System.IO.File.Open(String path, FileMode mode, FileAccess access, FileShare share) +58 ExcelLibrary.Office.CompoundDocumentFormat.CompoundDocument.Create(String file) +88 ExcelLibrary.Office.Excel.Workbook.Save(String file) +73 CHC_Reports.LitAnalysis.CreateSpreadSheet_Click(Object sender, EventArgs e) in C:\Users\brian\Desktop\Enterprise Manager\CHC_Reports\LitAnalysis.aspx.vb:19 System.Web.UI.WebControls.Button.OnClick(EventArgs e) +115 System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +140 System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +29 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +11041511 System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +11041050 System.Web.UI.Page.ProcessRequest() +91 System.Web.UI.Page.ProcessRequest(HttpContext context) +240 ASP.litanalysis_aspx.ProcessRequest(HttpContext context) +52 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +599 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +171 Any idea what I need to do to diagnose the permissions issue and allow the file creation? Thanks.

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  • .NET How would I build a DAL to meet my requirments?

    - by Jonno
    Assuming that I must deploy an asp.net app over the following 3 servers: 1) DB - not public 2) 'middle' - not public 3) Web server - public I am not allowed to connect from the web server to the DB directly. I must pass through 'middle' - this is purely to slow down an attacker if they breached the web server. All db access is via stored procedures. No table access. I simply want to provide the web server with a ado dataset (I know many will dislike this, but this is the requirement). Using asmx web services - it works, but XML serialisation is slow and it's an extra set of code to maintain and deploy. Using a ssh/vpn tunnel so that the one connects to the db 'via' the middle server, seems to remove any possible benefit of maintaining 'middle'. Using WCF binary/tcp removes the XML problem, but still there is extra code. Is there an approach that provides the ease of ssh/vpn, but the potential benefit of having the dal on the middle server? Many thanks.

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  • .NET - Is there a way to programmatically fill all tables in a strongly-typed dataset?

    - by Mike Loux
    Hello, all! I have a SQL Server database for which I have created a strongly-typed DataSet (using the DataSet Designer in Visual Studio 2008), so all the adapters and select commands and whatnot were created for me by the wizard. It's a small database with largely static data, so I would like to pull the contents of this DB in its entirety into my application at startup, and then grab individual pieces of data as needed using LINQ. Rather than hard-code each adapter Fill call, I would like to see if there is a way to automate this (possibly via Reflection). So, instead of: Dim _ds As New dsTest dsTestTableAdapters.Table1TableAdapter.Fill(_ds.Table1) dsTestTableAdapters.Table2TableAdapter.Fill(_ds.Table2) <etc etc etc> I would prefer to do something like: Dim _ds As New dsTest For Each tableName As String In _ds.Tables Dim adapter as Object = <routine to grab adapter associated with the table> adapter.Fill(tableName) Next Is that even remotely doable? I have done a fair amount of searching, and I wouldn't think this would be an uncommon request, but I must be either asking the wrong question, or I'm just weird to want to do this. I will admit that I usually prefer to use unbound controls and not go with strongly-typed datasets (I prefer to write SQL directly), but my company wants to go this route, so I'm researching it. I think the idea is that as tables are added, we can just refresh the DataSet using the Designer in Visual Studio and not have to make too many underlying DB code changes. Any help at all would be most appreciated. Thanks in advance!

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  • Passing a outside variable into a <asp:sqldatasource> tag. ASP.NET 2.0

    - by MadMAxJr
    I'm designing some VB based ASP.NET 2.0, and I am trying to make more use of the various ASP tags that visual studio provides, rather than hand writing everything in the code-behind. I want to pass in an outside variable from the Session to identify who the user is for the query. <asp:sqldatasource id="DataStores" runat="server" connectionstring="<%$ ConnectionStrings:MY_CONNECTION %>" providername="<%$ ConnectionStrings:MY_CONNECTION.ProviderName %>" selectcommand="SELECT THING1, THING2 FROM DATA_TABLE WHERE (THING2 IN (SELECT THING2 FROM RELATED_DATA_TABLE WHERE (USERNAME = @user)))" onselecting="Data_Stores_Selecting"> <SelectParameters> <asp:parameter name="user" defaultvalue ="" /> </SelectParameters> </asp:sqldatasource> And on my code behind I have: Protected Sub Data_Stores_Selecting(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.SqlDataSourceSelectingEventArgs) Handles Data_Stores.Selecting e.Command.Parameters("user").Value = Session("userid") End Sub Oracle squaks at me with ORA-01036, illegal variable name. Am I declaring the variable wrong in the query? I thought external variables share the same name with a @ prefixed. from what I understand, this should be placing the value I want into the query when it executes the select. EDIT: Okay, thanks for the advice so far, first error was corrected, I need to use : and not @ for the variable declaration in the query. Now it generates an ORA-01745 invalid host/bind variable name. EDIT AGAIN: Okay, looks like user was a reserved word. It works now! Thanks for other points of view on this one. I hadn't thought of that approach.

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  • Lucene.Net: How can I add a date filter to my search results?

    - by rockinthesixstring
    I've got my searcher working really well, however it does tend to return results that are obsolete. My site is much like NerdDinner whereby events in the past become irrelevant. I'm currently indexing like this Public Function AddIndex(ByVal searchableEvent As [Event]) As Boolean Implements ILuceneService.AddIndex Dim writer As New IndexWriter(luceneDirectory, New StandardAnalyzer(), False) Dim doc As Document = New Document doc.Add(New Field("id", searchableEvent.ID, Field.Store.YES, Field.Index.UN_TOKENIZED)) doc.Add(New Field("fullText", FullTextBuilder(searchableEvent), Field.Store.YES, Field.Index.TOKENIZED)) doc.Add(New Field("user", If(searchableEvent.User.UserName = Nothing, "User" & searchableEvent.User.ID, searchableEvent.User.UserName), Field.Store.YES, Field.Index.TOKENIZED)) doc.Add(New Field("title", searchableEvent.Title, Field.Store.YES, Field.Index.TOKENIZED)) doc.Add(New Field("location", searchableEvent.Location.Name, Field.Store.YES, Field.Index.TOKENIZED)) doc.Add(New Field("date", searchableEvent.EventDate, Field.Store.YES, Field.Index.UN_TOKENIZED)) writer.AddDocument(doc) writer.Optimize() writer.Close() Return True End Function Notice how I have a "date" index that stores the event date. My search then looks like this ''# code omitted Dim reader As IndexReader = IndexReader.Open(luceneDirectory) Dim searcher As IndexSearcher = New IndexSearcher(reader) Dim parser As QueryParser = New QueryParser("fullText", New StandardAnalyzer()) Dim query As Query = parser.Parse(q.ToLower) ''# We're using 10,000 as the maximum number of results to return ''# because I have a feeling that we'll never reach that full amount ''# anyways. And if we do, who in their right mind is going to page ''# through all of the results? Dim topDocs As TopDocs = searcher.Search(query, Nothing, 10000) Dim doc As Document = Nothing ''# loop through the topDocs and grab the appropriate 10 results based ''# on the submitted page number While i <= last AndAlso i < topDocs.totalHits doc = searcher.Doc(topDocs.scoreDocs(i).doc) IDList.Add(doc.[Get]("id")) i += 1 End While ''# code omitted I did try the following, but it was to no avail (threw a NullReferenceException). While i <= last AndAlso i < topDocs.totalHits If Date.Parse(doc.[Get]("date")) >= Date.Today Then doc = searcher.Doc(topDocs.scoreDocs(i).doc) IDList.Add(doc.[Get]("id")) i += 1 End If End While I also found the following documentation, but I can't make heads or tails of it http://lucene.apache.org/java/1_4_3/api/org/apache/lucene/search/DateFilter.html

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  • ASP.Net event only being raised every other time?

    - by eftpotrm
    I have an ASP.Net web user control which represents a single entry in a list. To allow users to reorder the items, each item has buttons to move the item up or down the list. Clicking on one of these raises an event to the parent page, which then shuffles the items in the placeholder control. Code fragments from the list entry: Public Event UpClicked As System.EventHandler Protected Sub btnUp_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnUp.Click RaiseEvent UpClicked(Me, New EventArgs()) End Sub And the parent container: rem (within the code to add an individual item to the placeholder) AddHandler l_oItem.UpClicked, AddressOf UpClicked Protected Sub UpClicked(ByVal sender As Object, ByVal e As EventArgs) MoveItem(DirectCast(sender, ScriptListItem), -1) End Sub It originally looked in testing like every other time the value for sender (verified by its properties) that reaches UpClicked is of an adjacent ListItem, not the one I've just clicked on - the first click is always wrong, then the second for the correct control. At present, testing appears to show that the button's click event is just being ignored every other time through. Breakpoints on the click events within the control simply aren't being hit, though the events are definitely being established. Why?

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  • Understanding C# async / await (1) Compilation

    - by Dixin
    Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is called MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been cleaned up so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# level syntax sugar. There is no difference to await a async method or a normal method. A method returning Task will be awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } The above code is already cleaned up, but there are still a lot of things. More clean up can be done, and the state machine can be very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> void IAsyncStateMachine.MoveNext() { try { switch (this.State) { // Orginal code is splitted by "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; IAsyncStateMachine this1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this1.MoveNext()); // Callback break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; IAsyncStateMachine this2 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => this2.MoveNext()); // Callback break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync_(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; (multiCallMethodAsyncStateMachine as IAsyncStateMachine).MoveNext(); // Original code are in this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clear - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback Since it is about callback, the simplification  can go even further – the entire state machine can be completely purged. Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is literally pretending to wait. In a await expression, a Task object will be return immediately so that caller is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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  • How I might think like a hacker so that I can anticipate security vulnerabilities in .NET or Java before a hacker hands me my hat [closed]

    - by Matthew Patrick Cashatt
    Premise I make a living developing web-based applications for all form-factors (mobile, tablet, laptop, etc). I make heavy use of SOA, and send and receive most data as JSON objects. Although most of my work is completed on the .NET or Java stacks, I am also recently delving into Node.js. This new stack has got me thinking that I know reasonably well how to secure applications using known facilities of .NET and Java, but I am woefully ignorant when it comes to best practices or, more importantly, the driving motivation behind the best practices. You see, as I gain more prominent clientele, I need to be able to assure them that their applications are secure and, in order to do that, I feel that I should learn to think like a malevolent hacker. What motivates a malevolent hacker: What is their prime mover? What is it that they are most after? Ultimately, the answer is money or notoriety I am sure, but I think it would be good to understand the nuanced motivators that lead to those ends: credit card numbers, damning information, corporate espionage, shutting down a highly visible site, etc. As an extension of question #1--but more specific--what are the things most likely to be seeked out by a hacker in almost any application? Passwords? Financial info? Profile data that will gain them access to other applications a user has joined? Let me be clear here. This is not judgement for or against the aforementioned motivations because that is not the goal of this post. I simply want to know what motivates a hacker regardless of our individual judgement. What are some heuristics followed to accomplish hacker goals? Ultimately specific processes would be great to know; however, in order to think like a hacker, I would really value your comments on the broader heuristics followed. For example: "A hacker always looks first for the low-hanging fruit such as http spoofing" or "In the absence of a CAPTCHA or other deterrent, a hacker will likely run a cracking script against a login prompt and then go from there." Possibly, "A hacker will try and attack a site via Foo (browser) first as it is known for Bar vulnerability. What are the most common hacks employed when following the common heuristics? Specifics here. Http spoofing, password cracking, SQL injection, etc. Disclaimer I am not a hacker, nor am I judging hackers (Heck--I even respect their ingenuity). I simply want to learn how I might think like a hacker so that I may begin to anticipate vulnerabilities before .NET or Java hands me a way to defend against them after the fact.

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  • Beginning programming for real clients, what copyright should I put in the code?

    - by Igor Marvinsky
    Hello. So far, I've been writing projects for my friends and friends of my friends, which required no legal stuff. Now I've moved on to freelance programming on websites like vworker.com and I'm wondering what should I put in the comments on top of the code. I'm not doing big, serious serious projects, just frontends and scrapers/bots for what I gather is personal use. Would my usual // Written by Igor Marvinsky, 2011 be enough?

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