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how-to-select-text-in-the-windows-forms-textbox-control.md

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title description ms.date dev_langs helpviewer_keywords ms.assetid
Select Text in TextBox Control
Learn how to select text programmatically in the Windows Forms TextBox control. Also learn how to visually alert the reader of the found string's position.
03/30/2017
csharp
vb
cpp
TextBox control [Windows Forms], selecting text programmatically
text boxes [Windows Forms], selecting text programmatically
text [Windows Forms], selecting in text boxes programmatically
8c591546-6a01-45c7-8e03-f78431f903b1

How to: Select Text in the Windows Forms TextBox Control

You can select text programmatically in the Windows Forms xref:System.Windows.Forms.TextBox control. For example, if you create a function that searches text for a particular string, you can select the text to visually alert the reader of the found string's position.

To select text programmatically

  1. Set the xref:System.Windows.Forms.TextBoxBase.SelectionStart%2A property to the beginning of the text you want to select.

    The xref:System.Windows.Forms.TextBoxBase.SelectionStart%2A property is a number that indicates the insertion point within the string of text, with 0 being the left-most position. If the xref:System.Windows.Forms.TextBoxBase.SelectionStart%2A property is set to a value equal to or greater than the number of characters in the text box, the insertion point is placed after the last character.

  2. Set the xref:System.Windows.Forms.TextBoxBase.SelectionLength%2A property to the length of the text you want to select.

    The xref:System.Windows.Forms.TextBoxBase.SelectionLength%2A property is a numeric value that sets the width of the insertion point. Setting the xref:System.Windows.Forms.TextBoxBase.SelectionLength%2A to a number greater than 0 causes that number of characters to be selected, starting from the current insertion point.

  3. (Optional) Access the selected text through the xref:System.Windows.Forms.TextBoxBase.SelectedText%2A property.

    The code below selects the contents of a text box when the control's xref:System.Windows.Forms.Control.Enter event occurs. This example checks if the text box has a value for the xref:System.Windows.Forms.TextBox.Text%2A property that is not null or an empty string. When the text box receives the focus, the current text in the text box is selected. The TextBox1_Enter event handler must be bound to the control; for more information, see How to: Create Event Handlers at Run Time for Windows Forms.

    To test this example, press the Tab key until the text box has the focus. If you click in the text box, the text is unselected.

    Private Sub TextBox1_Enter(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.Enter  
   If (Not String.IsNullOrEmpty(TextBox1.Text)) Then  
      TextBox1.SelectionStart = 0  
      TextBox1.SelectionLength = TextBox1.Text.Length  
   End If  
End Sub  
    private void textBox1_Enter(object sender, System.EventArgs e){  
   if (!String.IsNullOrEmpty(textBox1.Text))  
   {  
      textBox1.SelectionStart = 0;  
      textBox1.SelectionLength = textBox1.Text.Length;  
   }  
}  
    private:  
   void textBox1_Enter(System::Object ^ sender,  
      System::EventArgs ^ e) {  
   if (!System::String::IsNullOrEmpty(textBox1->Text))  
   {  
      textBox1->SelectionStart = 0;  
      textBox1->SelectionLength = textBox1->Text->Length;  
   }  
}

See also