WriteableBitmap::Unlock Method ()


Releases the back buffer to make it available for display.

Namespace:   System.Windows.Media.Imaging
Assembly:  PresentationCore (in PresentationCore.dll)

void Unlock()

Exception Condition

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

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.

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

// 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;

    // Reserve the back buffer for updates.

        // Get a pointer to the back buffer.
        int pBackBuffer = (int)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));

    // Release the back buffer and make it available for display.


for access to unmanaged resources. Security action: Demand. Associated enumeration: SecurityPermissionFlag::UnmanagedCode

.NET Framework
Available since 3.0
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