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  • C++ performance when accessing class members

    - by Dr. Acula
    I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } Does this basically result in similar code? Is there an extra overhead of accessing the class members? I'm sure that this is clear to an expert in C++ so I won't try and write an unrealistic benchmark for it right now

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  • Detecting if a file is binary or plain text?

    - by dr. evil
    How can I detect if a file is binary or a plain text? Basically my .NET app is processing batch files and extracting data however I don't want to process binary files. As a solution I'm thinking about analysing first X bytes of the file and if there are more unprintable characters than printable characters it should be binary. Is this the right way to do it? Is there nay better implementation for this task?

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  • How can I obtain the IP address of my server program?

    - by Dr Dork
    Hello! This question is related to another question I just posted. I'm prepping for a simple work project and am trying to familiarize myself with the basics of socket programming in a Unix dev environment. At this point, I have some basic server side code and client side code setup to communicate. Currently, my client code successfully connects to the server code and the server code sends it a test message, then both quit out. Perfect! That's exactly what I wanted to accomplish. Now I'm playing around with the functions used to obtain info about the two environments (server and client). I'd like to obtain my server program's IP address. Here's the code I currently have to do this, but it's not working... int sockfd; unsigned int len; socklen_t sin_size; char msg[]="test message"; char buf[MAXLEN]; int st, rv; struct addrinfo hints, *serverinfo, *p; struct sockaddr_storage client; char s[INET6_ADDRSTRLEN]; char ip[INET6_ADDRSTRLEN]; //zero struct memset(&hints,0,sizeof(hints)); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; //get the server info if((rv = getaddrinfo(NULL, SERVERPORT, &hints, &serverinfo ) != 0)){ perror("getaddrinfo"); exit(-1); } // loop through all the results and bind to the first we can for( p = serverinfo; p != NULL; p = p->ai_next) { //Setup the socket if( (sockfd = socket( p->ai_family, p->ai_socktype, p->ai_protocol )) == -1 ) { perror("socket"); continue; } //Associate a socket id with an address to which other processes can connect if(bind(sockfd, p->ai_addr, p->ai_addrlen) == -1){ close(sockfd); perror("bind"); continue; } break; } if( p == NULL ){ perror("Fail to bind"); } inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr), s, sizeof(s)); printf("Server has TCP Port %s and IP Address %s\n", SERVERPORT, s); and the output for the IP is always empty... server has TCP Port 21412 and IP Address :: any ideas for what I'm missing? thanks in advance for your help! this stuff is really complicated at first.

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  • is const (c++) optional?

    - by Dr Deo
    according to some tutorials i read a while back, the "const" declaration makes a variable "constant" ie it cannot change later. But i find this const declaration abit inconveniencing since the compiler sometimes gives errors like "cannot convert const int to int" or something like that. and i find myself cheating by removing it anyway. question: assuming that i am careful about not changing a variable in my source code, can i happily forget about this const stuff? Thanks in advance

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  • SQL Server 2005: Why would a delete from a temp table hang forever?

    - by Dr. Zim
    DELETE FROM #tItem_ID WHERE #tItem_ID.Item_ID NOT IN (SELECT DISTINCT Item_ID FROM Item_Keyword JOIN Keyword ON Item_Keyword.Keyword_ID = Keyword.Record_ID WHERE Keyword LIKE @tmpKW) The Keyword is %macaroni%. Both temp tables are 3300 items long. The inner select executes in under a second. All strings are nvarchar(249). All IDs are int. Any ideas? I executed it (it's in a stored proc) for over 12 minutes without it finishing.

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  • In an iPhone app, is it beneficial to tile a background image that has a pattern in it?

    - by Dr Dork
    Here's an example of the type of background image I'm talking about, the iPhone Notes app... Clearly, there's a pattern in it. My question is, if this were an iPad app and the background image was twice the size, would there be any significant benefits to taking advantage of this pattern by tiling the image? Or would it really make no difference in terms of performance and just be easier to load the entire image into a UIImageView? Thanks in advance for all your wisdom!

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  • Why can’t I create a database in an empty ASP MVC 2 project using Project->Add->New Item->SQL Server

    - by Dr Dork
    I'm diving head first into ASP MVC and am playing around with creating and manipulating a database. I did a search and found this tutorial for creating a database, however when I follow it, I get this error right at the start when trying to add a new database to my fresh, empty ASP MVC 2 project... A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) The only requirement the tutorial mentioned was SQL Server Express, but when I went to download it, it said it was already installed. I'm assuming it was part of the VS 2010 RC I installed and am running. So I don't know what else I need if I am missing something. This is all new to me, so I'm sure I'm missing something obvious here and after I'm done posting this question, I plan to do some more research into the topic of databases and how they work with ASP MVC. In the meantime, I was you could help me answer a couple high level questions... What am I missing/forgetting to do that is causing this error? Any suggestions for good resources/tutorials that focus on using databases with ASP MVC? I've done a lot of database programming in the past, so I'm familiar with the concepts of relational databases and the SQL language. I wish I could find a good resource for learning how to work with them in an ASP dev environment, as well as a good breakdown of all the related technologies used for working with them (i.e. LINQ to SQL). Thanks so much in advance for all your help! I'm going to start researching these questions right now.

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  • Performance when accessing class members

    - by Dr. Acula
    I'm writing something performance-critical and wanted to know if it could make a difference if I use: int test( int a, int b, int c ) { // Do millions of calculations with a, b, c } or class myStorage { public: int a, b, c; }; int test( myStorage values ) { // Do millions of calculations with values.a, values.b, values.c } Does this basically result in similar code? Is there an extra overhead of accessing the class members? I'm sure that this is clear to an expert in C++ so I won't try and write an unrealistic benchmark for it right now

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  • C#: Object having two constructors: how to limit which properties are set together?

    - by Dr. Zim
    Say you have a Price object that accepts either an (int quantity, decimal price) or a string containing "4/$3.99". Is there a way to limit which properties can be set together? Feel free to correct me in my logic below. The Test: A and B are equal to each other, but the C example should not be allowed. Thus the question How to enforce that all three parameters are not invoked as in the C example? AdPrice A = new AdPrice { priceText = "4/$3.99"}; // Valid AdPrice B = new AdPrice { qty = 4, price = 3.99m}; // Valid AdPrice C = new AdPrice { qty = 4, priceText = "2/$1.99", price = 3.99m};// Not The class: public class AdPrice { private int _qty; private decimal _price; private string _priceText; The constructors: public AdPrice () : this( qty: 0, price: 0.0m) {} // Default Constructor public AdPrice (int qty = 0, decimal price = 0.0m) { // Numbers only this.qty = qty; this.price = price; } public AdPrice (string priceText = "0/$0.00") { // String only this.priceText = priceText; } The Methods: private void SetPriceValues() { var matches = Regex.Match(_priceText, @"^\s?((?<qty>\d+)\s?/)?\s?[$]?\s?(?<price>[0-9]?\.?[0-9]?[0-9]?)"); if( matches.Success) { if (!Decimal.TryParse(matches.Groups["price"].Value, out this._price)) this._price = 0.0m; if (!Int32.TryParse(matches.Groups["qty"].Value, out this._qty)) this._qty = (this._price > 0 ? 1 : 0); else if (this._price > 0 && this._qty == 0) this._qty = 1; } } private void SetPriceString() { this._priceText = (this._qty > 1 ? this._qty.ToString() + '/' : "") + String.Format("{0:C}",this.price); } The Accessors: public int qty { get { return this._qty; } set { this._qty = value; this.SetPriceString(); } } public decimal price { get { return this._price; } set { this._price = value; this.SetPriceString(); } } public string priceText { get { return this._priceText; } set { this._priceText = value; this.SetPriceValues(); } } }

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  • How can I create a sample SQLLite DB for my iPhone app?

    - by Dr Dork
    I'm diving in to iPhone development and I'm building an iPhone app that uses the Core Data framework and my first task will be to get the model setup with a few that will display it. Thus far, I have the model defined and my Managed Object Files created, but I don't have a database with any sample data. What's a quick way to create a DB that conforms to my schema? Are there any tools that can generate a sample DB using my schemas? Is there a good tool I can use to directly manipulate the data in DB for testing purposes? Thanks in advance for your help! I'm going to continue researching this question right now.

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  • Starting a new Xcode project from a template vs. a blank project

    - by Dr Dork
    I sometimes find it's easier to create a new project from scratch in other IDEs simply because its often more difficult to understand and tweak the generated template code than it is to write the code you need from scratch. Do seasoned iPhone developers still use templates when creating new projects? How difficult is it to add functionality to a template project that isn't initially included in the template? For example, if I don't check the "Use Core Data" option when creating a new project, how difficult does that make it to use Core Data later on if I changed my mind?

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  • Using XSLT, how can I produce a table with elements at the position of the the node's attributes?

    - by Dr. Sbaitso
    Given the following XML: <items> <item> <name>A</name> <address>0</address> <start>0</start> <size>2</size> </item> <item> <name>B</name> <address>1</address> <start>2</start> <size>4</size> </item> <item> <name>C</name> <address>2</address> <start>5</start> <size>2</size> </item> </items> I want to generate the following output including colspan's +---------+------+------+------+------+------+------+------+------+ | Address | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | +---------+------+------+------+------+------+------+------+------+ | 0 | | | | | | | A | +---------+------+------+------+------+------+------+------+------+ | 1 | | | B | | | +---------+------+------+------+------+------+------+------+------+ | 2 | | C | | | | | | +---------+------+------+------+------+------+------+------+------+ | 3 | | | | | | | | | +---------+------+------+------+------+------+------+------+------+ I think I would be able to accomplish this with a mutable xslt variable, but alas, there's no such thing. Is it even possible? How?

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  • mysql not in my PATH for some reason

    - by Dr.Dredel
    I've installed mysql on several macs and on one of them mysql is not in the path. If I export it it shows up in the path correctly, but upon reboot, disappears. What should I do to get the machine to keep it in the path and what are the machines that DO have it in their path doing differently? Any thoughts appreciated.

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  • Enable/disable virtual keyboard

    - by dr.Xis
    I'm using a virtual keyboard. I have a checkbox that controls whether the virtual keyboard is displayed or not. The thing is that I don't understand how to disable it. I try to unbind it but it doesn't work... I also tried to use namespaces and then unbind all namespaces but still the keyboard remains accessible after a click on the text box. <input class="virtualKeyboardField ui-keyboard-input ui-widget-content ui-corner-all" data-val="true" data-val-required="The User name field is required." id="loginUserName" name="UserName" type="text" value="" aria-haspopup="true" role="textbox"> <script type="text/javascript"> $(function () { //show login $("#showLogin").on({ click: function () { $("#loginFormDiv").toggle("slow"); } }); $("#cb_showVKey").on('click', CheckIsToShowKey); }); function CheckIsToShowKey(event) { //var isCheck = $("#cb_showVKey").is(':checked'); //alert("ischecked? " + isCheck); if ($("#cb_showVKey").is(':checked')) { //if checked BindKeyboards(); } else { //not checked UnBindKeyboards(); } } function bindVirtualKeyboards() { $("#loginForm").delegate(".virtualKeyboardField", "click.xpto", BindKeyboards); } function UnBindKeyboards() { $("#loginForm").undelegate(".virtualKeyboardField", "click.xpto", BindKeyboards); } function BindKeyboards() { // alert(event.currentTarget.id); //alert("xpto"); if ($("#cb_showVKey").is(':checked')) { $("#loginUserName").keyboard({ layout: 'qwerty', lockInput: true, preventPaste: true }); $("#loginUserPassword").keyboard({ layout: 'qwerty', lockInput: true, preventPaste: true }); } } $(document).ready(function () { $("#loginForm").validate(); BindKeyboards(); }); </script> Any help guys?

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  • Three customer addresses in one table or in separate tables?

    - by DR
    In my application I have a Customer class and an Address class. The Customer class has three instances of the Address class: customerAddress, deliveryAddress, invoiceAddress. Whats the best way to reflect this structure in a database? The straightforward way would be a customer table and a separate address table. A more denormalized way would be just a customer table with columns for every address (Example for "street": customer_street, delivery_street, invoice_street) What are your experiences with that? Are there any advantages and disadvantages of these approaches?

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  • Can a thread call wait() on two locks at once in Java (6)

    - by Dr. Monkey
    I've just been messing around with threads in Java to get my head around them (it seems like the best way to do so) and now understand what's going on with synchronize, wait() and notify(). I'm curious about whether there's a way to wait() on two resources at once. I think the following won't quite do what I'm thinking of: synchronized(token1) { synchronized(token2) { token1.wait(); token2.wait(); //won't run until token1 is returned System.out.println("I got both tokens back"); } } In this (very contrived) case token2 will be held until token1 is returned, then token1 will be held until token2 is returned. The goal is to release both token1 and token2, then resume when both are available (note that moving the token1.wait() outside the inner synchronized loop is not what I'm getting at). A loop checking whether both are available might be more appropriate to achieve this behaviour (would this be getting near the idea of double-check locking?), but would use up extra resources - I'm not after a definitive solution since this is just to satisfy my curiosity.

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  • Read StandardOutput Process from BackgroundWorkerProcess method

    - by Nicola Celiento
    Hi all, I'm working with a BackgroundWorker Process from Windows .NET C# application. From the async method I call many instance of cmd.exe Process (foreach), and read from StandardOutput, but at the 3-times cycle the ReadToEnd() method throw Timeout Exception. Here the code: StreamWriter sw = null; DataTable dt2 = null; StringBuilder result = null; Process p = null; for(DataRow dr in dt1.Rows) { arrLine = new string[4]; //new row result = new StringBuilder(); arrLine[0] = dr["ID"].ToString(); arrLine[1] = dr["ChangeSet"].ToString(); #region Initialize Process CMD p = new Process(); ProcessStartInfo info = new ProcessStartInfo(); info.FileName = "cmd.exe"; info.CreateNoWindow = true; info.RedirectStandardInput = true; info.RedirectStandardOutput = true; info.RedirectStandardError = true; info.UseShellExecute = false; p.StartInfo = info; p.Start(); sw = new StreamWriter(p.StandardInput.BaseStream); #endregion using (sw) { if (sw.BaseStream.CanWrite) { sw.WriteLine("cd " + this.path_WORKDIR); sw.WriteLine("tfpt getcs /changeset:" + arrLine[1]); } } string strError = p.StandardError.ReadToEnd(); // Read shell error output commmand (TIMEOUT) result.Append(p.StandardOutput.ReadToEnd()); // Read shell output commmand sw.Close(); sw.Dispose(); p.Close(); p.Dispose(); } Timeout is on code line: string strError = p.StandardError.ReadToEnd(); Can you help me? Thanks!

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  • can't commit or rollback, MySQL out of sync error on .net

    - by sergiogx
    Im having trouble with a stored procedure, I can't commit after I execute it. Its showing this error "[System.Data.Odbc.OdbcException] = {"ERROR [HY000] [MySQL][ODBC 5.1 Driver]Commands out of sync; you can't run this command now"}" The SP by itself works fine. does anyone have idea of what might be happening? .net code: [WebMethod()] [SoapHeader("sesion")] public Boolean aceptarTasaCero(int idMunicipio, double valor) { Boolean resultado = false; OdbcConnection cxn = new OdbcConnection(); cxn.ConnectionString = ConfigurationManager.ConnectionStrings["mysqlConnection"].ConnectionString; cxn.Open(); OdbcCommand cmd = new OdbcCommand("call aceptarTasaCero(?,?)", cxn); cmd.Parameters.Add("idMunicipio", OdbcType.Int).Value = idMunicipio; cmd.Parameters.Add("valor", OdbcType.Double).Value = valor; cmd.Transaction = cxn.BeginTransaction(); try { OdbcDataReader dr = cmd.ExecuteReader(); if (dr.Read()) { resultado = Convert.ToBoolean(dr[0]); } cmd.Transaction.Commit(); } catch (Exception ex) { ExBi.log(ex, sesion.idUsuario); cmd.Transaction.Rollback(); } finally { cxn.Close(); } return resultado; } and this is the code for the stored procedure DELIMITER $$ DROP PROCEDURE IF EXISTS `aceptartasacero` $$ CREATE DEFINER=`database`@`%` PROCEDURE `aceptartasacero`(pidMun INTEGER, pvalor double) BEGIN declare vExito BOOLEAN; INSERT INTO tasacero(anio,valor,idmunicipios) VALUES(YEAR(curdate()),pValor,pidMun); set vExito = true; select vExito; END $$ DELIMITER ; thanks.

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  • WPF Toolkit: Nullable object must have a value

    - by Via Lactea
    Hi All, I am trying to create some line charts from a dataset and getting an error (WPF+WPF Toolkit + C#): Nullable object must have a value Here is a code that I use to add some data points to the chart: ObservableCollection points = new ObservableCollection(); foreach (DataRow dr in dc.Tables[0].Rows) { points.Add(new VelChartPoint() { Label = dr[0].ToString(), Value = double.Parse(dr[1].ToString()) }); } Here is a class VelChartPoint public class VelChartPoint : VelObject, INotifyPropertyChanged { public DateTime Date { get; set; } public string Label { get; set; } private double _Value; public double Value { get { return _Value; } set { _Value = value; var handler = PropertyChanged; if (null != handler) { handler.Invoke(this, new PropertyChangedEventArgs("Value")); } } } public string FieldName { get; set; } public event PropertyChangedEventHandler PropertyChanged; public VelChartPoint() { } } So the problem occures in this part of the code points.Add(new VelChartPoint { Name = dc.Tables[0].Rows[0][0].ToString(), Value = double.Parse(dc.Tables[0].Rows[0][1].ToString()) } ); I've made some tests, here are some results i've found out. This part of code does'nt work for me: string[] labels = new string[] { "label1", "label2", "label3" }; foreach (string label in labels) { points.Add(new VelChartPoint { Name = label, Value = 500.0 } ); } But this one works fine: points.Add(new VelChartPoint { Name = "LabelText", Value = double.Parse(dc.Tables[0].Rows[0][1].ToString()) } ); Please, help me to solve this error.

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  • CommandBuilder and SqlTransaction to insert/update a row

    - by Jesse
    I can get this to work, but I feel as though I'm not doing it properly. The first time this runs, it works as intended, and a new row is inserted where "thisField" contains "doesntExist" However, if I run it a subsequent time, I get a run-time error that I can't insert a duplicate key as it violate the primary key "thisField". static void Main(string[] args) { using(var sqlConn = new SqlConnection(connString) ) { sqlConn.Open(); var dt = new DataTable(); var sqlda = new SqlDataAdapter("SELECT * FROM table WHERE thisField ='doesntExist'", sqlConn); sqlda.Fill(dt); DataRow dr = dt.NewRow(); dr["thisField"] = "doesntExist"; //Primary key dt.Rows.Add(dr); //dt.AcceptChanges(); //I thought this may fix the problem. It didn't. var sqlTrans = sqlConn.BeginTransaction(); try { sqlda.SelectCommand = new SqlCommand("SELECT * FROM table WITH (HOLDLOCK, ROWLOCK) WHERE thisField = 'doesntExist'", sqlConn, sqlTrans); SqlCommandBuilder sqlCb = new SqlCommandBuilder(sqlda); sqlda.InsertCommand = sqlCb.GetInsertCommand(); sqlda.InsertCommand.Transaction = sqlTrans; sqlda.DeleteCommand = sqlCb.GetDeleteCommand(); sqlda.DeleteCommand.Transaction = sqlTrans; sqlda.UpdateCommand = sqlCb.GetUpdateCommand(); sqlda.UpdateCommand.Transaction = sqlTrans; sqlda.Update(dt); sqlTrans.Commit(); } catch (Exception) { //... } } } Even when I can get that working through trial and error of moving AcceptChanges around, or encapsulating changes within Begin/EndEdit, then I begin to experience a "Concurrency violation" in which it won't update the changes, but rather tell me it failed to update 0 of 1 affected rows. Is there something crazy obvious I'm missing?

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  • How to download .txt file from a url?

    - by Colin Roe
    I produced a text file and is saved to a location in the project folder. How do I redirect them to the url that contains that text file, so they can download the text file. CreateCSVFile creates the csv file to a file path based on a datatable. Calling: string pth = ("C:\\Work\\PG\\AI Handheld Website\\AI Handheld Website\\Reports\\Files\\report.txt"); CreateCSVFile(data, pth); And the function: public void CreateCSVFile(DataTable dt, string strFilePath) { StreamWriter sw = new StreamWriter(strFilePath, false); int iColCount = dt.Columns.Count; for (int i = 0; i < iColCount; i++) { sw.Write(dt.Columns[i]); if (i < iColCount - 1) { sw.Write(","); } } sw.Write(sw.NewLine); // Now write all the rows. foreach (DataRow dr in dt.Rows) { for (int i = 0; i < iColCount; i++) { if (!Convert.IsDBNull(dr[i])) { sw.Write(dr[i].ToString()); } if (i < iColCount - 1) { sw.Write(","); } } sw.Write(sw.NewLine); } sw.Close(); Response.WriteFile(strFilePath); FileInfo fileInfo = new FileInfo(strFilePath); if (fileInfo.Exists) { //Response.Clear(); //Response.AddHeader("Content-Disposition", "attachment; filename=" + fileInfo.Name); //Response.AddHeader("Content-Length", fileInfo.Length.ToString()); //Response.ContentType = "application/octet-stream"; //Response.Flush(); //Response.TransmitFile(fileInfo.FullName); } }

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  • Using A Local file path in a Streamwriter object ASP.Net

    - by Nick LaMarca
    I am trying to create a csv file of some data. I have wrote a function that successfully does this.... Private Sub CreateCSVFile(ByVal dt As DataTable, ByVal strFilePath As String) Dim sw As New StreamWriter(strFilePath, False) ''# First we will write the headers. ''EDataTable dt = m_dsProducts.Tables[0]; Dim iColCount As Integer = dt.Columns.Count For i As Integer = 0 To iColCount - 1 sw.Write(dt.Columns(i)) If i < iColCount - 1 Then sw.Write(",") End If Next sw.Write(sw.NewLine) ''# Now write all the rows. For Each dr As DataRow In dt.Rows For i As Integer = 0 To iColCount - 1 If Not Convert.IsDBNull(dr(i)) Then sw.Write(dr(i).ToString()) End If If i < iColCount - 1 Then sw.Write(",") End If Next sw.Write(sw.NewLine) Next sw.Close() End Sub The problem is I am not using the streamwriter object correctly for what I trying to accomplish. Since this is an asp.net I need the user to pick a local filepath to put the file on. If I pass any path to this function its gonna try to write it to the directory specified on the server where the code is. I would like this to popup and let the user select a place on their local machine to put the file.... Dim exData As Byte() = File.ReadAllBytes(Server.MapPath(eio)) File.Delete(Server.MapPath(eio)) Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", fn)) Response.ContentType = "application/x-msexcel" Response.BinaryWrite(exData) Response.Flush() Response.End() I am calling the first function in code like this... Dim emplTable As DataTable = SiteAccess.DownloadEmployee_H() CreateCSVFile(emplTable, "C:\\EmplTable.csv") Where I dont want to have specify the file loaction (because this will put the file on the server and not on a client machine) but rather let the user select the location on their client machine. Can someone help me put this together? Thanks in advance.

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