# CreateRectRgn

### C# Signature:

```cs
[DllImport("gdi32.dll")]
static extern IntPtr CreateRectRgn(int nLeftRect, int nTopRect, int nRightRect, int nBottomRect);
```

### VB.NET Signature:

```cs
<DllImport("gdi32.dll")> _
Private Shared Function CreateRectRgn(ByVal nLeftRect As Integer, ByVal nTopRect As Integer, ByVal nRightRect As Integer, ByVal nBottomRect As Integer) As IntPtr
End Function
```

### Sample Code:

```cs
[DllImport("user32.dll",EntryPoint="GetDC")]
        static extern IntPtr GetDC(IntPtr hWnd);

        [DllImport("gdi32.dll")]
        static extern bool FillRgn(IntPtr hdc, IntPtr hrgn, IntPtr hbr);

        [DllImport("gdi32.dll")]
        static extern IntPtr CreateRectRgn(int nLeftRect, int nTopRect, int nRightRect,
            int nBottomRect);

        [DllImport("gdi32.dll")]
        static extern IntPtr CreateSolidBrush(uint crColor);

        [DllImport("gdi32.dll")]
        static extern bool DeleteObject(IntPtr hObject);
```

### Sample Code:

```cs
// This paints the current form black
                IntPtr wDc = GetDC(this.Handle);
                int mx = Screen.PrimaryScreen.WorkingArea.Width;
                int my = Screen.PrimaryScreen.WorkingArea.Height;
                IntPtr brush = CreateSolidBrush(0x0); // black, of format : //0x00bbggrr 
                FillRgn(wDc, CreateRectRgn(0,0,mx,my), brush);
                DeleteObject(brush);
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://pinvokeisalive.gitbook.io/pinvoke/desktopfunctions/gdi32/createrectrgn.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.