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  • Filter the datagridview column based on the current row of another column in C#

    - by user286546
    I have a datagridview that is populating columns from different table. I want to filter the column based on another column of the current row. I tried to use the cell enter event of the datagridview and then filtered the column by filtering the binding source on the column of the current row. private void lINKDataGridView_CellEnter(object sender, DataGridViewCellEventArgs e) { this.pROBLEMBindingSource.Filter = "item_id = " + this.lINKDataGridView.Rows[e.RowIndex].Cells[dataGridViewTextBoxColumn4.Index].Value + ""; } This is how I am filtering the "problem " binding source on the cell enter event of the datagridview . It is working fine but I am getting an error- being: System.ArgumentException: DataGridViewComboBoxCell value is not valid. Any suggestion

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  • How to view a Column Name in listbox by selecting the Column in DataGridView

    - by Umair
    Hey, im working on a project and i have to get the name(header text) of selected column in my listbox or textbox from datagridview, when i select any column it shows the name of that column in textbox or listbox.. i'll be very thankful to if you guys kindly help me out in this matter.. im trying to use the code on DataGridViewHeaderClickEvent "textBox1.Text=dataGridView1.SelectedColumns.ToString();"

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  • Is there any functional difference between immutable value types and immutable reference types?

    - by Kendall Frey
    Value types are types which do not have an identity. When one variable is modified, other instances are not. Using Javascript syntax as an example, here is how a value type works. var foo = { a: 42 }; var bar = foo; bar.a = 0; // foo.a is still 42 Reference types are types which do have an identity. When one variable is modified, other instances are as well. Here is how a reference type works. var foo = { a: 42 }; var bar = foo; bar.a = 0; // foo.a is now 0 Note how the example uses mutatable objects to show the difference. If the objects were immutable, you couldn't do that, so that kind of testing for value/reference types doesn't work. Is there any functional difference between immutable value types and immutable reference types? Is there any algorithm that can tell the difference between a reference type and a value type if they are immutable? Reflection is cheating. I'm wondering this mostly out of curiosity.

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  • Nullable types and ?? operator C# [en-US]

    - by ruimachado
    Nullable types vs Non-nullable types   While developing our C# projects its frequent the null comparison operation to avoid null exceptions. This simple operation is mainly coded using the "var x = null" code example inside an if clause. However not all types of variables are nullable, which means that setting a variable to null is not allowed in every cases, it depends on what kind of type are you defining. But what if there was an extension to your non-nullable type that would convert your variable types to nullable? This extension really exists. As I said before in C# you have nullable types which represent all the values of an underlying type, and an additional null value and can be declared easily using "T?", where T is the type of the variable and for example the normal int type cannot be null, so its a non-nullable type, however if you define a "int?" your variable can be null, what you do is convert a non-nullable type to a nullable type. Example: int x=null;     Not allowed     int? x=null;   Allowed     While using nullable types you can check if a variable is null the same way you do it with nullable types:     But what about setting a default value when a certain variable is null?   In this cases the c# .net framework let you set a default value when you try to assign a nullable type to a non-nullable type, using the ?? operator. If you don't use this operator you can still catch the InvalidOperationException which is throw in this cases. For example  without the ?? operator :     Using the ?? operator your code becomes cleaner and more easy to read and you get a bonus, you can set a default value for multiple variables using the ?? in a chain set.     That’s it,   Thanks, Rui Machado rpmachado.wordpress.com

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  • Edit/Access data from a CheckBox column in an ASPX:GridView - c#

    - by Endo
    Hi, I have a GridView to which I bind a dataTable I manually create. Both the GridView and the dataTable contain 2 columns, Name and isBusy. My GridView looks like this <Columns> <asp:BoundField HeaderText="Name" DataField="Name" SortExpression="Name"> </asp:BoundField> <asp:CheckBoxField DataField="isBusy" HeaderText="Busy" SortExpression="isBusy" /> </Columns> That works fine, except that the Busy column is non-editable unless you set a specific row to edit mode. I require the entire column of checkboxes to be checkable. So I converted the column to a template, and so the columns look like this: <Columns> <asp:BoundField HeaderText="Name" DataField="Name" SortExpression="Name"> </asp:BoundField> <asp:TemplateField HeaderText="Busy" SortExpression="isBusy"> <ItemTemplate> <asp:CheckBox ID="isBusy" runat="server" Checked='<%# Eval("isBusy") %>' oncheckedchanged="CheckBoxBusy_CheckedChanged" /> </ItemTemplate> </asp:TemplateField> </Columns> Now, this throws an error at runtime, saying System.InvalidCastException was unhandled by user code Message="Specified cast is not valid." Source="App_Web_zzjsqlrr" StackTrace: at ASP.proyectos_aspx.__DataBinding__control24(Object sender, EventArgs e) in c:\Proyect\Users.aspx:line 189 at System.Web.UI.Control.OnDataBinding(EventArgs e) at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding) at System.Web.UI.Control.DataBind() at System.Web.UI.Control.DataBindChildren() InnerException: Any idea why this is happening? The next step I would need is to know how to set and get a checkbox's state (haven't been able to find how to manually check a checkbox). I appreciate very much any help.

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  • Converting to a column oriented array in Java

    - by halfwarp
    Although I have Java in the title, this could be for any OO language. I'd like to know a few new ideas to improve the performance of something I'm trying to do. I have a method that is constantly receiving an Object[] array. I need to split the Objects in this array through multiple arrays (List or something), so that I have an independent list for each column of all arrays the method receives. Example: List<List<Object>> column-oriented = new ArrayList<ArrayList<Object>>(); public void newObject(Object[] obj) { for(int i = 0; i < obj.length; i++) { column-oriented.get(i).add(obj[i]); } } Note: For simplicity I've omitted the initialization of objects and stuff. The code I've shown above is slow of course. I've already tried a few other things, but would like to hear some new ideas. How would you do this knowing it's very performance sensitive?

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  • Cannot iterate of a collection of Anonymous Types created from a LINQ Query in VB.NET

    - by Atari2600
    Ok everyone, I must be missing something here. Every LINQ example I have seen for VB.NET anonymous types claims I can do something like this: Dim Info As EnumerableRowCollection = pDataSet.Tables(0).AsEnumerable Dim Infos = From a In Info _ Select New With {.Prop1 = a("Prop1"), .Prop2 = a("Prop2"), .Prop3 = a("Prop3") } Now when I go to iterate through the collection(see example below), I get an error that says "Name "x" is not declared. For Each x in Infos ... Next It's like VB.NET doesn't understand that Infos is a collection of anonymous types created by LINQ and wants me to declare "x" as some type. (Wouldn't this defeat the purpose of an anonymous type?) I have added the references to System.Data.Linq and System.Data.DataSetExtensions to my project. Here is what I am importing with the class: Imports System.Linq Imports System.Linq.Enumerable Imports System.Linq.Queryable Imports System.Data.Linq Any ideas?

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  • C++ Types Impossible to Name

    - by Kirakun
    While reading Wikipedia's page on decltype, I was curious about the statement, Its [decltype's] primary intended use is in generic programming, where it is often difficult, or even impossible, to name types that depend on template parameters. While I can understand the difficulty part of that statement, what is an example where there is a need to name a type that cannot be named under C++03? EDIT: My point is that since everything in C++ has a declaration of types. Why would there ever be a case where it is impossible to name a type? Furthermore, aren't trait classes designed to yield type informations? Could trait classes be an alternative to decltype?

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  • C#: Get key and value types of non-generic IDictionary at runtime

    - by Yang Zou
    there. I am wondering how I can get the key and value types of a non-generic IDictionary at runtime. For generic IDictionary, we can use reflection to get the generic arguments, which has been answered here. But for non-generic IDictionary, for instance, HybridDictionary, how can I get the key and value types? Thanks. Edit: I may not describe my problem properly. For non-generic IDictionary, if I have HyBridDictionary, which is declared as HyBridDictionary dict = new HyBridDictionary(); dict.Add("foo" , 1); dict.Add("bar", 2); How can I find out the type of the key is string and type of the value is int? Did I make the question clear? Thanks.

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  • assembly.GetTypes() does not return all types

    - by meta
    I try to lead the types from an .dll (which is also referenced in the executing project). I call: public static void LoadPlugin(string pluginFile) { Assembly assembly = Assembly.LoadFrom(pluginFile); foreach (Type type in assembly.GetTypes()) { // play with it } } It loads just a few of them: public partial class Mathematics : UserControl, IMathematics, IPortable and public partial class Welcome : UserControl but the next one, and some others, are ignored: public partial class Test : UserControl, ITest, IPortable They all stand in the same assembly, under the same namespace. The public static void LoadPlugin(string pluginFile) method is located in other assembly that is also referenced in the executing project. No exceptions are thrown. What could be the issues for not loading all the types? Any ideas?

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  • Altering a Column Which has a Default Constraint

    - by Dinesh Asanka
    Setting up a default column is a common task for  developers.  But, are we naming those default constraints explicitly? In the below  table creation, for the column, sys_DateTime the default value Getdate() will be allocated. CREATE TABLE SampleTable (ID int identity(1,1), Sys_DateTime Datetime DEFAULT getdate() ) We can check the relevant information from the system catalogs from following query. SELECT sc.name TableName, dc.name DefaultName, dc.definition, OBJECT_NAME(dc.parent_object_id) TableName, dc.is_system_named  FROM sys.default_constraints dc INNER JOIN sys.columns sc ON dc.parent_object_id = sc.object_id AND dc.parent_column_id = sc.column_id and results would be: Most of the above columns are self-explanatory. The last column, is_system_named, is to identify whether the default name was given by the system. As you know, in the above case, since we didn’t provide  any default name, the  system will generate a default name for you. But the problem with these names is that they can differ from environment to environment.  If example if I create this table in different table the default name could be DF__SampleTab__Sys_D__7E6CC920 Now let us create another default and explicitly name it: CREATE TABLE SampleTable2 (ID int identity(1,1), Sys_DateTime Datetime )   ALTER TABLE SampleTable2 ADD CONSTRAINT DF_sys_DateTime_Getdate DEFAULT( Getdate()) FOR Sys_DateTime If we run the previous query again we will be returned the below output. And you can see that last created default name has 0 for is_system_named. Now let us say I want to change the data type of the sys_DateTime column to something else: ALTER TABLE SampleTable2 ALTER COLUMN Sys_DateTime Date This will generate the below error: Msg 5074, Level 16, State 1, Line 1 The object ‘DF_sys_DateTime_Getdate’ is dependent on column ‘Sys_DateTime’. Msg 4922, Level 16, State 9, Line 1 ALTER TABLE ALTER COLUMN Sys_DateTime failed because one or more objects access this column. This means, you need to drop the default constraint before altering it: ALTER TABLE [dbo].[SampleTable2] DROP CONSTRAINT [DF_sys_DateTime_Getdate] ALTER TABLE SampleTable2 ALTER COLUMN Sys_DateTime Date   ALTER TABLE [dbo].[SampleTable2] ADD CONSTRAINT [DF_sys_DateTime_Getdate] DEFAULT (getdate()) FOR [Sys_DateTime] If you have a system named default constraint that can differ from environment to environment and so you cannot drop it as before, you can use the below code template: DECLARE @defaultname VARCHAR(255) DECLARE @executesql VARCHAR(1000)   SELECT @defaultname = dc.name FROM sys.default_constraints dc INNER JOIN sys.columns sc ON dc.parent_object_id = sc.object_id AND dc.parent_column_id = sc.column_id WHERE OBJECT_NAME (parent_object_id) = 'SampleTable' AND sc.name ='Sys_DateTime' SET @executesql = 'ALTER TABLE SampleTable DROP CONSTRAINT ' + @defaultname EXEC( @executesql) ALTER TABLE SampleTable ALTER COLUMN Sys_DateTime Date ALTER TABLE [dbo].[SampleTable] ADD DEFAULT (Getdate()) FOR [Sys_DateTime]

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  • Indexing only one MySQL column value

    - by BrainCore
    I have a MySQL InnoDB table with a status column. The status can be 'done' or 'processing'. As the table grows, at most .1% of the status values will be 'processing,' whereas the other 99.9% of the values will be 'done.' This seems like a great candidate for an index due to the high selectivity for 'processing' (though not for 'done'). Is it possible to create an index for the status column that only indexes the value 'processing'? I do not want the index to waste an enormous amount of space indexing 'done.'

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  • Identity column SQL Server 2005 inserting same value twice

    - by DannykPowell
    I have a stored procedure that inserts into a table (where there is an identity column that is not the primary key- the PK is inserted initially using the date/time to generate a unique value). We then use SCOPEIDENTITY() to get the value inserted, then there is some logic to generate the primary key field value based on this value, which is then updated back to the table. In some situations the stored procedure is called simultaneously by more than one process, resulting in "Violation of PRIMARY KEY constraint..." errors. This would seem to indicate that the identity column is allowing the same number to be inserted for more than one record. First question- how is this possible? Second question- how to stop it...there's no error handling currently so I'm going to add some try/ catch logic- but would like to understand the problem fully to deal with properly

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  • f# types' properties in inconsistent order and of slightly differing types

    - by philbrowndotcom
    I'm trying to iterate through an array of objects and recursively print out each objects properties. Here is my object model: type firmIdentifier = { firmId: int ; firmName: string ; } type authorIdentifier = { authorId: int ; authorName: string ; firm: firmIdentifier ; } type denormalizedSuggestedTradeRecommendations = { id: int ; ticker: string ; direction: string ; author: authorIdentifier ; } Here is how I am instantiating my objects: let getMyIdeasIdeas = [| {id=1; ticker="msfqt"; direction="buy"; author={authorId=0; authorName="john Smith"; firm={firmId=12; firmName="Firm1"}};}; {id=2; ticker="goog"; direction="sell"; author={authorId=1; authorName="Bill Jones"; firm={firmId=13; firmName="ABC Financial"}};}; {id=3; ticker="DFHF"; direction="buy"; author={authorId=2; authorName="Ron James"; firm={firmId=2; firmName="DEFFirm"}};}|] And here is my algorithm to iterate, recurse and print: let rec recurseObj (sb : StringBuilder) o= let props : PropertyInfo [] = o.GetType().GetProperties() sb.Append( o.GetType().ToString()) |> ignore for x in props do let getMethod = x.GetGetMethod() let value = getMethod.Invoke(o, Array.empty) ignore <| match value with | :? float | :? int | :? string | :? bool as f -> sb.Append(x.Name + ": " + f.ToString() + "," ) |> ignore | _ -> recurseObj sb value for x in getMyIdeas do recurseObj sb x sb.Append("\r\n") |> ignore If you couldnt tell, I'm trying to create a csv file and am printing out the types for debugging purposes. The problem is, the first element comes through in the order you'd expect, but all subsequent elements come through with a slightly different (and confusing) ordering of the "child" properties like so: RpcMethods+denormalizedSuggestedTradeRecommendationsid: 1,ticker: msfqt,direction: buy,RpcMethods+authorIdentifierauthorId: 0,authorName: john Smith,RpcMethods+firmIdentifierfirmId: 12,firmName: Firm1, RpcMethods+denormalizedSuggestedTradeRecommendationsid: 2,ticker: goog,direction: sell,RpcMethods+authorIdentifierauthorName: Bill Jones,RpcMethods+firmIdentifierfirmName: ABC Financial,firmId: 13,authorId: 1, RpcMethods+denormalizedSuggestedTradeRecommendationsid: 3,ticker: DFHF,direction: buy,RpcMethods+authorIdentifierauthorName: Ron James,RpcMethods+firmIdentifierfirmName: DEFFirm,firmId: 2,authorId: 2, Any idea what is going on here?

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  • Query a column and a calculation of columns at the same time PostgreSQL

    - by pablo
    Hi I have two tables, Products and BundleProducts that have o2o relation with BaseProducts. A BundleProduct is a collection of Products using a m2m realtion to the Products table. Products has a price column and the price of a BundleProduct is calculated as the sum of the prices of its Products. BaseProducts have columns like name and description so I can query it to get both Products and BundleProducts. Is it possible to query and sort by price both for the price column of the Products and calculated price of the BundleProducts? Thanks

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  • Compute column widths in a HTML-like manner (based on cell contents)

    - by cipak
    Hi, I have a grid of data that I want to export to RTF, PDF etc. using various (and not perfect) PHP converters/generators. What I am missing most is the HTML table automatic adjustment of column widths based on the lengths of strings in the cells (strings contain line breaks which complicate things a bit, as they should be preserved). I need an algorithm that, given the contents of the cells (plain text), a total width of the table and an average width of a character, would return a width for each column. I wouldn't want to reinvent the wheel if something is already available. Of course it can't be perfect if the font is variable width, but an approximation would do just fine. Or maybe it could have a configurable table with widths for each character. Any hint would be appreciated. Thank you.

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  • Instantiating a list of parameterized types, making beter use of Generics and Linq

    - by DanO
    I'm hashing a file with one or more hash algorithms. When I tried to parametrize which hash types I want, it got a lot messier than I was hoping. I think I'm missing a chance to make better use of generics or LINQ. I also don't like that I have to use a Type[] as the parameter instead of limiting it to a more specific set of type (HashAlgorithm descendants), I'd like to specify types as the parameter and let this method do the constructing, but maybe this would look better if I had the caller new-up instances of HashAlgorithm to pass in? public List<string> ComputeMultipleHashesOnFile(string filename, Type[] hashClassTypes) { var hashClassInstances = new List<HashAlgorithm>(); var cryptoStreams = new List<CryptoStream>(); FileStream fs = File.OpenRead(filename); Stream cryptoStream = fs; foreach (var hashClassType in hashClassTypes) { object obj = Activator.CreateInstance(hashClassType); var cs = new CryptoStream(cryptoStream, (HashAlgorithm)obj, CryptoStreamMode.Read); hashClassInstances.Add((HashAlgorithm)obj); cryptoStreams.Add(cs); cryptoStream = cs; } CryptoStream cs1 = cryptoStreams.Last(); byte[] scratch = new byte[1 << 16]; int bytesRead; do { bytesRead = cs1.Read(scratch, 0, scratch.Length); } while (bytesRead > 0); foreach (var stream in cryptoStreams) { stream.Close(); } foreach (var hashClassInstance in hashClassInstances) { Console.WriteLine("{0} hash = {1}", hashClassInstance.ToString(), HexStr(hashClassInstance.Hash).ToLower()); } }

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  • C# 4: Real-World Example of Dynamic Types

    - by routeNpingme
    I think I have my brain halfway wrapped around the Dynamic Types concept in C# 4, but can't for the life of me figure out a scenario where I'd actually want to use it. I'm sure there are many, but I'm just having trouble making the connection as to how I could engineer a solution that is better solved with dynamics as opposed to interfaces, dependency injection, etc. So, what's a real-world application scenario where dynamic type usage is appropriate?

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  • Silverlight 4 Data Binding with anonymous types.

    - by Anthony
    Does anyone know if you can use data binding with anonymous types in Silverlight 4? I know you can't in previous versions of silverlight, you can only databind to public class properties and anonymous type properties are internal. Just wondering if anyone has tried it in silverlight 4? Thanks in advanced

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