# RectangleF.Union Method (RectangleF, RectangleF)

.NET Framework (current version)

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Creates the smallest possible third rectangle that can contain both of two rectangles that form a union.

Namespace:   System.Drawing
Assembly:  System.Drawing (in System.Drawing.dll)

## Syntax

```public static RectangleF Union(
RectangleF a,
RectangleF b
)
```

#### Parameters

a
Type: System.Drawing.RectangleF

A rectangle to union.

b
Type: System.Drawing.RectangleF

A rectangle to union.

#### Return Value

Type: System.Drawing.RectangleF

A third RectangleF structure that contains both of the two rectangles that form the union.

## Remarks

When one of the two rectangles is empty, meaning all of its values are zero, the Union method returns a rectangle with a starting point of (0, 0), and the height and width of the non-empty rectangle. For example, if you have two rectangles A = (0, 0; 0, 0) and B = (1, 1; 2, 2), then the union of A and B is (0, 0; 2, 2).

## Examples

This example is designed for use with Windows Forms, and it requires PaintEventArgs e, an OnPaint event object. The code creates two RectangleF s and draws them to the screen in black and red. Notice that they have to be converted to Rectangle s for drawing purposes. Then the code creates a third RectangleF using the Union method, converts it to a Rectangle, and draws it to the screen in blue. Notice the third (blue) rectangle is the smallest possible rectangle that can contain both of the other two rectangles:

```public void RectangleFUnionExample(PaintEventArgs e)
{

// Create two rectangles and draw them to the screen.
RectangleF firstRectangleF = new RectangleF(0, 0, 75, 50);
RectangleF secondRectangleF = new RectangleF(100, 100, 20, 20);

// Convert the RectangleF structures to Rectangle structures and draw them to the

// screen.
Rectangle firstRect = Rectangle.Truncate(firstRectangleF);
Rectangle secondRect = Rectangle.Truncate(secondRectangleF);
e.Graphics.DrawRectangle(Pens.Black, firstRect);
e.Graphics.DrawRectangle(Pens.Red, secondRect);

// Get the union rectangle.
RectangleF unionRectangleF = RectangleF.Union(firstRectangleF,
secondRectangleF);

// Draw the unionRectangleF to the screen.
Rectangle unionRect = Rectangle.Truncate(unionRectangleF);
e.Graphics.DrawRectangle(Pens.Blue, unionRect);
}
```

## Version Information

.NET Framework
Available since 1.1

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