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  • How can I make a DateTimePicker display an empty string?

    - by brass-kazoo
    I would like to be able to display a DateTimePicker that has a default value of nothing, i.e. no date. For example, I have a start date dtTaskStart and an end date dtTaskEnd for a task, but the end date is not known, and not populated initially. I have specified a custom format of yyyy-MM-dd for both controls. Setting the value to null, or an empty string at runtime causes an error, so how can I accomplish this? I have considered using a checkbox to control the enabling of this field, but there is still the issue of displaying an initial value.. Edit: Arguably a duplicate of the question DateTimePicker Null Value (.NET), but the solution I found for my problem is not a solution for that question, so I think it should remain here for others to find..

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  • Why does my call to Activator.CreateInstance intermittently fail?

    - by Daniel Stutzbach
    I'm using the following code to access the Windows Explorer Shell's band site service: Guid GUID_TrayBandSiteService = new Guid(0xF60AD0A0, 0xE5E1, 0x45cb, 0xB5, 0x1A, 0xE1, 0x5B, 0x9F, 0x8B, 0x29, 0x34); Type shellTrayBandSiteService = Type.GetTypeFromCLSID(GUID_TrayBandSiteService, true); site = Activator.CreateInstance(shellTrayBandSiteService) as IBandSite; Mostly, it works great. A very small percentage of the time (less than 1%), the call to Activator.CreateInstance throws the following exception: System.Runtime.InteropServices.COMException (0x80040154): Retrieving the COM class factory for component with CLSID {F60AD0A0-E5E1-45CB-B51A-E15B9F8B2934} failed due to the following error: 80040154. at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck) at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache) at System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache) at System.Activator.CreateInstance(Type type, Boolean nonPublic) I've looked up the error code, and it appears to indicate that the service isn't registered. That's nonsense in my case, since I'm trying to access a service provided by the operating system (explorer.exe, to be specific). I'm stumped. What might cause Activator.CreateInstance fail, but only rarely?

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  • C# Win Forms Auto-Updating Controls

    - by Goober
    Hello! I have a datagridview and a combobox which get populated randomly with data. However, the new data is never displayed automatically. Someone mentioned the idea of invalidating the control to force the application to redraw it and thus iterate through the contents and populate the control with the new data. Does anyone know which is the best method for implementing auto-updating controls in windows forms applications? help greatly appreciated, regards.

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  • When to use MVP in Windows Forms .net application?

    - by Janalopa
    I am familiar with MVC/MVP though my question is simple, I'm about to program a simple Instant Messaging software when the engine and communication part is an open API. so my software will have about 3 forms, a splash screen with login details, the options form and a main form with all the functionality like: Friends List, Send message, Received messages (tabbed), search user, etc. In UI perspective, its important for the GUI to be in 1 form in my application. So my question is, for the only complicated form that I'm going to have, is it necessary to implement an MVP design pattern or in this case its better to just go straight forward and put all the logic in 1 place? THANKS Janalopa!

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  • How do I display a DataGridView within a cell of another datagridview in C# forms app?

    - by Sachin
    How do I display a DataGridView within a cell of another datagridview in C# forms app? How would I have to handle Sorting & value changed if this possible? That is the only way I can display data to make some sense.. Think of it like I have a task column and dates column. Under the dates column I have a list of things to be done. These date columns are dynamic & there might be multiple date columns Thanks, Sachin

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  • Passing data to a non-static listBox, by calling function from another class

    - by Andrew A
    I have a simple forms program that I have been fighting with for a while now. I simply want to be able to call a method from a different class file (when a certain step is triggered in the code in that class file) in order to insert a string in the listBox. Here is my main method, pretty standard: class Program { [STAThread] static void Main(string[] args) { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(new MainForm()); } } Here is the function which resides in my MainForm.cs file, which I can call just fine from that class file (via 'TextToBox(myString);'): public partial class MainForm : Form { ... // Function to output results to main Listbox window public void TextToBox(string aString) { // Place messages in Main Display list box window this.listBox1.Items.Insert(0, aString); } ... } But my problem is when I am in another class and I want to call 'TextToBox(myString);'. If I create another object reference of the MainForm, the code compiles fine but nothing will show up in the listBox. How do I do this? I cannot simply make TextToBox() static. I know I must create the object reference but I can't figure out how to reference the ORIGINAL MainForm, the one that was created in the Main method. Thanks in advance...

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  • What's the simplest way to ask for user input through Modal in Win Form

    - by Refracted Paladin
    What is the simplest way to implement a Modal(popup) MessageBox that allows a custom value to be entered and returned. In my case, a String. Maybe I am over thinking this but I figured I'd ask. I plan to just create a new Form. Add a label, a textbox, two buttons. Assign the textbox to a property and from my main form call a ShowDialog() on it. Will I be able to still access the property that way or should I somehow return the value? Is this a decent way of doing this?

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  • 2 sided winform Tree - exist?

    - by Avi Harush
    Hi, I'm looking for a 2 sided winform Tree control. something like what you see in the math books. meaning that the tree can go both right and left in the control. Something like http://www.math.bas.bg/~nkirov/2010/NETB201/slides/ch06/pic3.jpg Thanks Avi

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  • Slow Databinding setup time in C# .NET 4.0

    - by Svisstack
    Hello, I have got a problem. I have windows forms application with dynamic generated layout, but i have a problem in performance. In this form i use DataBinding from .NET 4.0 and databinding after setup works fine, but he binding setup time for ONE control blocking my application on approx 0.7 second. I have some controls and time of binging setuping is around 2 minutes. I trying all possible solutions, I dont have any ideas without write self binding class. Why is wrong with my code? case "Boolean": { Binding b = new Binding("Checked", __bindingsource, __ep.Name); CheckBox cb = new CheckBox(); /* * HERE is the problem */ cb.DataBindings.Add(b); /* * HERE is the end of problem */ __flp.Controls.Add(cb); __bindingcontrol.AddBinding(b); break; } Without problem code lines all works fast and without binding ;-( but i want binding turn on in normal speed. PS1. I have suspended layout in generation time. PS2. I have same problem with binding TextBox'es, PictureBoxe's, CheckBox is only example. How to do that?

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  • Bound checkbox does not update its datasource.

    - by Scott Chamberlain
    I have a checkbox who's checked value is bound to a binding source which is bound to a boolean data table column. When I click my save button to push my changes in my data table to my sql server the value in the data table is never changed. Designer code. this.cbxKeepWebInfinityChanges = new System.Windows.Forms.CheckBox(); this.preProductionBindingSource = new System.Windows.Forms.BindingSource(); // // cbxKeepWebInfinityChanges // this.cbxKeepWebInfinityChanges.AutoSize = true; this.cbxKeepWebInfinityChanges.DataBindings.Add(new System.Windows.Forms.Binding("Checked", this.preProductionBindingSource, "WEBINFINTY_CHANGES", true, System.Windows.Forms.DataSourceUpdateMode.OnPropertyChanged)); this.cbxKeepWebInfinityChanges.Location = new System.Drawing.Point(6, 98); this.cbxKeepWebInfinityChanges.Name = "cbxKeepWebInfinityChanges"; this.cbxKeepWebInfinityChanges.Size = new System.Drawing.Size(152, 17); this.cbxKeepWebInfinityChanges.TabIndex = 30; this.cbxKeepWebInfinityChanges.Text = "Keep WebInfinity Changes"; this.cbxKeepWebInfinityChanges.UseVisualStyleBackColor = true; this.cbxKeepWebInfinityChanges.CheckedChanged += new System.EventHandler(this.CauseApplyChangesActivation); // // preProductionBindingSource // this.preProductionBindingSource.AllowNew = false; this.preProductionBindingSource.DataMember = "PreProduction"; this.preProductionBindingSource.DataSource = this.salesLogix; Save Code //the comments are the debugger values before the call in going from checked when loaded to unchecked when saved. private void btnApplyChanges_Click(object sender, EventArgs e) { (...) // non related saving logic for other controls preProductionBindingSource.EndEdit(); // checked = false, databinding = true, datatable = true preProductionTableAdapter.Update(salesLogix.PreProduction); // checked = false, databinding = true, datatable = true } After the saving code the box rechecks itself. The same things happens when going from unchecked to checked. does not save the change and reverts to the old value. Other items I have bound to the same data-binding source (I have two combo boxes) are updating correctly.

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  • DataGridView's top left cell value is not displayed.

    - by Spike
    I have a DataGridView, without visible row or column headers, and bound to a BindingList. No matter what I try the top left cell (Rows[0].Cells[0]) is always empty. The cell's Visible property is true, but it never displays its contents. If I make some rows and columns invisible, it's still the top left of the visible cells that isn't displayed.

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  • Form gets disposed somehow

    - by mnn
    I have a client-server application, in which I use classic Sockets and threads for receiving/sending data and listening for clients. The application works fine, but after some random time I get the ObjectDisposedException: System.ObjectDisposedException: Cannot access a disposed object. Object name: 'MainForm'. at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous) at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args) at System.Windows.Forms.Control.Invoke(Delegate method) That code is called from client Socket thread and I use Invoke() method to run the code on UI thread. I'm sure that I don't manually dispose the form nor using Close() (form is closed by user clicking Close button), so I don't know what could cause its disposing.

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  • How to dispose of variables in windows close button

    - by cmrhema
    Hi, I have a windows forms application, where I have declared some static variables. On the click of exit button, I have disposed of some datatable which i have declared static. Many a times the user instead of clicking the exit button, will just exit the windows application by clicking the X button on the left corner top. What should be done to ensure that even if the user clicks the X button, everything is disposed of properly. Thanks Regards Hema

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  • Prevent deferred creation of controls.

    - by Scott Chamberlain
    Here is a test framework to show what I am doing, just create a new project add a tabbed control, on tab 1 put a button on tab 2 put a check box (default names) and paste this code for its code public partial class Form1 : Form { private List<bool> boolList = new List<bool>(); BindingSource bs = new BindingSource(); public Form1() { InitializeComponent(); boolList.Add(false); bs.DataSource = boolList; checkBox1.DataBindings.Add("Checked", bs, ""); } bool updating = false; private void button1_Click(object sender, EventArgs e) { updating = true; boolList[0] = true; bs.ResetBindings(false); Application.DoEvents(); updating = false; } private void checkBox1_CheckedChanged(object sender, EventArgs e) { if (!updating) MessageBox.Show("CheckChanged fired outside of updating"); } } The issue is if you run the program and look at tab 2 then press the button on tab 1 the program works as expected, however if you press the button on tab 1 then look at tab 2 the event for the checkbox will not fire untill you look at tab 2. The reason for this is the controll on tab 2 is not in the "created" state, so its binding to change the checkbox from unchecked to checked does not happen until after the control has been "Created". checkbox1.CreateControl() does not do anything because according to MSDN CreateControl does not create a control handle if the control's Visible property is false. You can either call the CreateHandle method or access the Handle property to create the control's handle regardless of the control's visibility, but in this case, no window handles are created for the control's children. I tried getting the value of Handle(there is no CreateHandle for Button) but still the same result. Any suggestions other than have the program quickly flash all of my tabs that have data-bound check boxes when it first loads?

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  • winform - login form template

    - by BhejaFry
    Hi folks, new to winform development. I am trying to add a 'login form' to my project in vs2008 but the template is missing. When i do 'add new item', i don't see 'login form'. However i do see mainform, aboutbox form templates. TIA

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  • Problem with flash in a webbrowser in a winform

    - by fgnt
    I have the oddest problem (but aren't all programming problems odd?). I have a winform that contains a webbrowser object that opens a website that has flash on it. This winform is running on a touchscreen computer (I can't find the brand or model number). Here is what I know: flash objects embeded in a website that is accessed via the webbrowser object in my winform do not function properly said flash objects only react to the first 'click' on them. So the website opens and if I hit a button, that button works but nothing afterward works within the flash object works. If my first 'click' misses a button, nothing works there after. trying to 'click' an flash button gives the same response as just hovering over the button This isn't a problem with the touch part of the touch screen as using a mouse also gives the same not working right response this isn't a problem with the web page as I can open up explorer on the same computer and navigate the webpage just fine from there The program also works 100% right on my personal computer so it shouldn't be the program's fault if it's not the touch screen fault and not the program's fault, I can't blame anything right now. the EXACT same program worked 100% on our old touch screen (which was having other problems so we had to get rid of it). Oh, also, surfing just a 'normal' webpage in a webbrowser in the winform works just fine.

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  • Positioning problem in VIsta when Aero Theme is enabled

    - by Adeel Rehman
    Hi, I have a Windows form which has tab pages. On a Tab Page, I have a Combo Box. When I click the combobox a drop down opens up just below the combo box to give the impression of a drop down. The drop down is a windows form and this is how I set its position Popup.Location = control.PointToScreen(parentcontrol.PointToClient(new System.Drawing.Point(0, control.Height))); Popup = drop down that opens below the combo box (Windows Form) control = my combo box (Combo Box) parentcontrol = the windows form on which the control is present (Parent Form) Problem:- The X coordinate is not plotted correctly on the screen with Aero theme enabled. This works perfectly fine on XP (with some variance in y due to tablelayout panel i assume). But when i use the same code on Vista with Aero theme enabled the x-cordinate wanders away about 20-30 pixels. If I Turn Aero theme off on Vista, it works fine. I have found the X and Y coordiantes calculated in both cases are the same. But the way Vista draws these coordinates on the screen (when aero theme is enabled) is different. Is there any solution to this problem? Thanks, Adeel Rehman.

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  • What's wrong with my cross-thread call in Windows Forms?

    - by MainMa
    Hi, I encounter a problem with a Windows Forms application. A form must be displayed from another thread. So in the form class, I have the following code: private delegate void DisplayDialogCallback(); public void DisplayDialog() { if (this.InvokeRequired) { this.Invoke(new DisplayDialogCallback(DisplayDialog)); } else { this.ShowDialog(); } } Now, every time I run this, an InvalidOperationException is thrown on the line this.ShowDialog();: "Cross-thread operation not valid: Control 'SampleForm' accessed from a thread other than the thread it was created on." What's wrong with this piece of code? Isn't it a valid way to make cross-thread calls? Is there something special with ShowDialog()?

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  • System.Windows.Forms.DataVisualization Namespace Fine in One Class but Not in Another

    - by jxpx777
    Hi. I'm getting this error The type or namespace name 'DataVisualization' does not exist in the namespace 'System.Windows.Forms' (are you missing an assembly reference?) Here is my using section of the class: using System; using System.Collections; using System.Collections.Generic; using System.Windows.Forms.DataVisualization.Charting; using System.Windows.Forms.DataVisualization.Charting.Borders3D; using System.Windows.Forms.DataVisualization.Charting.ChartTypes; using System.Windows.Forms.DataVisualization.Charting.Data; using System.Windows.Forms.DataVisualization.Charting.Formulas; using System.Windows.Forms.DataVisualization.Charting.Utilities; namespace myNamespace { public class myClass { // Usual class stuff } } The thing is that I am using the same DataVisualization includes in another class. The only thing that I can think that is different is that the classes that are giving this missing namespace error are Solution Items rather than specific to a project. The projects reference them by link. Anyone have thoughts on what the problem is? I've installed the chart component, .Net 3.5 SP1, and the Chart Add-in for Visual Studio 2008. UPDATE: I moved the items from Solution Items to be regular members of my project and I'm still seeing the same behavior. UPDATE 2: Removing the items from the Solution Items and placing them under my project worked. Another project was still referencing the files which is why I didn't think it worked previously. I'm still curious, though, why I couldn't use the namespace when the classes were Solution Items but moving them underneath a project (with no modifications, mind you) instantly made them recognizable. :\

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  • Windows Screensaver Multi Monitor Problem

    - by Bryan
    I have a simple screensaver that I've written, which has been deployed to all of our company's client PCs. As most of our PCs have dual monitors, I took care to ensure that the screensaver ran on both displays. This works fine, however on some systems, where the primary screen has been swapped (to the left monitor), the screensaver only works on the left (primary) screen. The offending code is below. Can anyone see anything I've done wrong, or a better way of handling this? For info, the context of "this", is the screensaver form itself. // Make form full screen and on top of all other forms int minY = 0; int maxY = 0; int maxX = 0; int minX = 0; foreach (Screen screen in Screen.AllScreens) { // Find the bounds of all screens attached to the system if (screen.Bounds.Left < minX) minX = screen.Bounds.Left; if (screen.Bounds.Width > maxX) maxX = screen.Bounds.Width; if (screen.Bounds.Bottom < minY) minY = screen.Bounds.Bottom; if (screen.Bounds.Height > maxY) maxY = screen.Bounds.Height; } // Set the location and size of the form, so that it // fills the bounds of all screens attached to the system Location = new Point(minX, minY); Height = maxY - minY; Width = maxX - minX; Cursor.Hide(); TopMost = true;

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  • VS2008 Windows Form Designer does not like my control.

    - by Thedric Walker
    I have a control that is created like so: public partial class MYControl : MyControlBase { public string InnerText { get { return textBox1.Text; } set { textBox1.Text = value; } } public MYControl() { InitializeComponent(); } } partial class MYControl { /// <summary> /// Required designer variable. /// </summary> private System.ComponentModel.IContainer components = null; /// <summary> /// Clean up any resources being used. /// </summary> /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param> protected override void Dispose(bool disposing) { if (disposing && (components != null)) { components.Dispose(); } base.Dispose(disposing); } #region Component Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { this.textBox1 = new System.Windows.Forms.TextBox(); this.listBox1 = new System.Windows.Forms.ListBox(); this.label1 = new System.Windows.Forms.Label(); this.SuspendLayout(); // // textBox1 // this.textBox1.Location = new System.Drawing.Point(28, 61); this.textBox1.Name = "textBox1"; this.textBox1.Size = new System.Drawing.Size(100, 20); this.textBox1.TabIndex = 0; // // listBox1 // this.listBox1.FormattingEnabled = true; this.listBox1.Location = new System.Drawing.Point(7, 106); this.listBox1.Name = "listBox1"; this.listBox1.Size = new System.Drawing.Size(120, 95); this.listBox1.TabIndex = 1; // // label1 // this.label1.AutoSize = true; this.label1.Location = new System.Drawing.Point(91, 42); this.label1.Name = "label1"; this.label1.Size = new System.Drawing.Size(35, 13); this.label1.TabIndex = 2; this.label1.Text = "label1"; // // MYControl // this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F); this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font; this.Controls.Add(this.label1); this.Controls.Add(this.listBox1); this.Controls.Add(this.textBox1); this.Name = "MYControl"; this.Size = new System.Drawing.Size(135, 214); this.ResumeLayout(false); this.PerformLayout(); } #endregion private System.Windows.Forms.Label label1; } MyControlBase contains the definition for the ListBox and TextBox. Now when I try to view this control in the Form Designer it gives me these errors: The variable 'listBox1' is either undeclared or was never assigned. The variable 'textBox1' is either undeclared or was never assigned. This is obviously wrong as they are defined in MyControlBase with public access. Is there any way to massage Form Designer into allowing me to visually edit my control?

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  • How to draw a rectangle in WinForm app in the correct location

    - by TooFat
    I have a WinForm app that has an image displayed in a PictureBox that has the added functionality of allowing a user to draw a rectangle on the image by clicking and dragging. The Location, Height and Width of the rectangle are saved to disk. When the image is viewed again I would like to automatically redraw that rectangle in the same position on the image. When I redraw it, however, the Height and Width are fine but the location is always off. The location is being captured in the MouseDown Event like so private void pbSample_MouseDown(object Sender, MouseEventArgs e) { if (SelectMode) { StartLocation.X = e.X; StartLocation.Y = e.Y; //later on these are saved as the location of the rectangle } } And I am redrawing it like so public void DrawSelectedArea(Rectangle rect) { Graphics g = this.PictureBox1.CreateGraphics(); Pen p = new Pen(Brushes.Black); g.DrawRectangle(p, rect); } Given the location from the MouseEventArgs captured during the MouseDown Event how can I calculate the correct location to redraw my rectangle?

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