Windows Forms - Page 2

Use this code to restrict users to launching only one instance of an application.

Learn how to bind Windows Forms controls to each other can reduce the code and logic needed to synchronize color changes between controls in a Windows Form.

This code sets the Windows desktop wallpaper to an arbitrary image on the user's local drive. It illustrates use of VB2005 "My" classes, in this case to find the location of the user's My Pictures directory without a lot of coding.

Use the ComboBox Created Property to determine if a combobox is being loaded or not.

Return the Tag value of the selected RadioButton from the input array of controls. This is useful when you have many radio buttons, with a value associated to each one, and want to select the value of the checked option. Instead of writing something like this: If RadioButton1.Checked Then

Most document-based applications typically allow to open a document file in two ways: with the Open File menu command / toolbar button, or by dragging and dropping the file from Windows Explorer to the application's window. This works with MS Word, Winzip and many other applications. ...

Enable the key-skipping mechanism for the input TextBox and for the input chars Example: don't process the 'A', 'b' and '0' chars EnableTextBoxCharSkip(TextBox1, "A"c, "b"c, "0"c)

Find all the controls with the specified Tag value Example: Dim ctrls() As Control = GetControlsByTag("OK", Me) Dim ctrl As Control For Each ctrl In ctrls Debug.WriteLine(ctrl.Name) Next

Determine the current line in a multiline TextBox control Example: MessageBox.Show(GetTextBoxCurrentLine(TextBox1))

Have you ever tried to change the BorderStyle, HideSelection, MultiLine, ScrollBars, WordWrap and TextAlign properties of a TextBox, or the ComboBox

Return a reference to the control with the specified name, searched into the specified container and its sub-controls Note: it requires the GetAllControls function Example: get a reference to a Label named "lblTest", and set its Text property DirectCast(FindControl("lblTest", Me), Label).

Create an InputBox like the one of VB6. You can define the dialog's title, question and default value. Example: MessageBox.Show(InputDialog.InputBox("Type your name:", "Test", "Marco"))

Insert an image into a RichTextBox, in the current position This version takes in input the target RichTextBox and the path of the image to insert Example: InsertImageIntoRtb(RichTextBox1, "C:\test.jpg")

It happens quite often that you have a DataGrid with hidden columns (with width = 0), because you need their values but don't want to show them to the user. However, when you tab through the DataGrid's columns, these "hidden" columns are still taken into account in the tab order. This means ...

Returns an array with all the controls in the specified container control and its child containers Example: print the name of all the controls on the form and its child container controls Dim ctl As Control For Each ctl In GetAllControls(Me) Debug.WriteLine(ctl.Name) Next

Return a validation summary string with all the error messages, if any, of the controls inside the specified container, associated to an ErrorProvider control Example: Dim summary As String = "" display the validation summary for all the controls on the form summary = GetValid

Returns an array of controls of the specified type, found within the specified parent control (or the form itself). Note: the search is optionally done recursively, by checking also controls' child controls Example: get an array with the form's textboxes Dim textboxes() As TextBox = ...

Resets the value for the input array of controls, and thier child controls Example: - reset all the controls on the form: ResetControls(Me) - reset specific controls: ResetControls(TextBox1, CheckBox1, GroupBox1)

Returns the nesting level of a TreeView's Node object (returns zero for root nodes)