WriteableBitmap.Unlock Method

Definition

Namespace:

System.Windows.Media.Imaging

Assembly:

PresentationCore.dll

Releases the back buffer to make it available for display.

C#

public void Unlock();

Exceptions

InvalidOperationException

The bitmap has not been locked by a call to the Lock() or TryLock(Duration) methods.

Examples

The following code example shows how to release the back buffer by using the Unlock method.

C#

    // The DrawPixel method updates the WriteableBitmap by using
    // unsafe code to write a pixel into the back buffer.
    static void DrawPixel(MouseEventArgs e)
    {
        int column = (int)e.GetPosition(i).X;
        int row = (int)e.GetPosition(i).Y;

        try{
            // Reserve the back buffer for updates.
            writeableBitmap.Lock();

            unsafe
            {
                // Get a pointer to the back buffer.
                IntPtr pBackBuffer = writeableBitmap.BackBuffer;

                // Find the address of the pixel to draw.
                pBackBuffer += row * writeableBitmap.BackBufferStride;
                pBackBuffer += column * 4;

                // Compute the pixel's color.
                int color_data = 255 << 16; // R
                color_data |= 128 << 8;   // G
                color_data |= 255 << 0;   // B

                // Assign the color data to the pixel.
                *((int*) pBackBuffer) = color_data;
            }

            // Specify the area of the bitmap that changed.
            writeableBitmap.AddDirtyRect(new Int32Rect(column, row, 1, 1));
        }
        finally{
            // Release the back buffer and make it available for display.
            writeableBitmap.Unlock();
        }
    }

Remarks

The Unlock method decrements the lock count. When the lock count reaches 0, a render pass is requested if the AddDirtyRect method has been called.

Applies to

See also

• Lock()
• AddDirtyRect(Int32Rect)