C# Tip Article

Problem

One of my blog readers asked why he was unable to call Control.Invoke() in Form constuctor. Calling Invoke() method in Form constructor (or after form is closed/disposed) causes an error "Invoke or BeginInvoke cannot be called on a control until the window handle has been created."

	public Form1()
	{
		InitializeComponent();

		// Error
		this.button1.Invoke((MethodInvoker)delegate
		{
			this.button1.Text = "OK";
		});
	}

Solution

Invoke or BeginInvoke method can be called on a control when the control has window handle. Window handles for the child controls are created after Form is loaded/shown. So the fix is to move the code in Form_Load event handler or somewhere after the window handle is created.

	public Form1()
	{
		InitializeComponent();
	}

	private void Form1_Load(object sender, EventArgs e)
	{
		// No Error
		this.button1.Invoke((MethodInvoker)delegate
		{
			this.button1.Text = "OK";
		});
	}

By the way, there is no reason to use Invoke() method in the example above. This is for illustration purpose only.