Control.CreateGraphics Method

Definition

Namespace:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Source:

Control.cs

Creates the Graphics for the control.

public:
 System::Drawing::Graphics ^ CreateGraphics();

public System.Drawing.Graphics CreateGraphics ();

member this.CreateGraphics : unit -> System.Drawing.Graphics

Public Function CreateGraphics () As Graphics

Returns

Graphics

The Graphics for the control.

Examples

The following code example resizes the specified control so the control will accommodate its formatted text. The formatted text is the Text property with the control's assigned Font applied to the text. The AutoSizeControl method in this example also has a textPadding parameter that represents the padding to apply to all edges of the control. To make the padding appear equal, align the text with the MiddleCenter value of System.Drawing.ContentAlignment if your control supports it.

private:
   void AutoSizeControl( Control^ control, int textPadding )
   {
      
      // Create a Graphics object for the Control.
      Graphics^ g = control->CreateGraphics();
      
      // Get the Size needed to accommodate the formatted Text.
      System::Drawing::Size preferredSize = g->MeasureString( control->Text, control->Font ).ToSize();
      
      // Pad the text and resize the control.
      control->ClientSize = System::Drawing::Size( preferredSize.Width + (textPadding * 2), preferredSize.Height + (textPadding * 2) );
      
      // Clean up the Graphics object.
      delete g;
   }

private void AutoSizeControl(Control control, int textPadding)
{
   // Create a Graphics object for the Control.
   Graphics g = control.CreateGraphics();

   // Get the Size needed to accommodate the formatted Text.
   Size preferredSize = g.MeasureString(
      control.Text, control.Font).ToSize();

   // Pad the text and resize the control.
   control.ClientSize = new Size(
      preferredSize.Width + (textPadding * 2), 
      preferredSize.Height+(textPadding * 2) );

   // Clean up the Graphics object.
   g.Dispose();
}

Private Sub AutoSizeControl(control As Control, textPadding As Integer)
   ' Create a Graphics object for the Control.
   Dim g As Graphics = control.CreateGraphics()
   
   ' Get the Size needed to accommodate the formatted Text.
   Dim preferredSize As Size = g.MeasureString( _
     control.Text, control.Font).ToSize()
   
   ' Pad the text and resize the control.
   control.ClientSize = New Size( _
     preferredSize.Width + textPadding * 2, _
     preferredSize.Height + textPadding * 2)
   
   ' Clean up the Graphics object.
   g.Dispose()
End Sub

Remarks

The Graphics object that you retrieve through the CreateGraphics method should not normally be retained after the current Windows message has been processed, because anything painted with that object will be erased with the next WM_PAINT message. Therefore you cannot cache the Graphics object for reuse, except to use non-visual methods like Graphics.MeasureString. Instead, you must call CreateGraphics every time that you want to use the Graphics object, and then call Dispose when you are finished using it. For more information about Windows messages, see WndProc.

By design, CreateGraphics sets ownership to the calling thread, and fails if it is called on other threads.

Note

In addition to the InvokeRequired property, there are four methods on a control that are thread safe: Invoke, BeginInvoke, EndInvoke, and CreateGraphics if the handle for the control has already been created. Calling CreateGraphics before the control's handle has been created on a background thread can cause illegal cross thread calls. For all other method calls, you should use one of the invoke methods to marshal the call to the control's thread.

See also

• Graphics