C # Fill the rectangle with custom or specified colors

It seems that the Graphics. FillRectangle method can only be filled with a Brush.

GOOGLE has two methods: 1. Linear Gradient Filling

 

  public void FillByColor(Rectangle rect,Color c,Graphics G)
{
    System.Drawing.Drawing2D.LinearGradientBrush lBrush = new System.Drawing.Drawing2D.LinearGradientBrush(rect, c, c, 0);
    G.FillRectangle(lBrush, rect);
}

Reference: How to: create a linear gradient

2. Use APIs to fill a closed area with a specified color(Not tested) Use API to implement specified color Filling

 using System.Runtime.InteropServices;
[DllImport("gdi32.dll")]
public static extern IntPtr SelectObject(IntPtr hdc, IntPtr hgdiobj);

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

[DllImport("gdi32.dll")]
public static extern bool ExtFloodFill(IntPtr hdc, int nXStart, int nYStart, int crColor, uint fuFillType);

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

[DllImport("gdi32.dll")]
public static extern int GetPixel(IntPtr hdc, int x, int y);

public static uint FLOODFILLBORDER = 0;
public static uint FLOODFILLSURFACE = 1;

private void button1_Click(object sender, EventArgs e)
{
    Graphics vGraphics = Graphics.FromHwnd(Handle);
    vGraphics.DrawRectangle(Pens.Blue, new Rectangle(0, 0, 300, 300));
    vGraphics.DrawRectangle(Pens.Blue, new Rectangle(50, 70, 300, 300));
    IntPtr vDC = vGraphics.GetHdc();
    IntPtr vBrush = CreateSolidBrush(ColorTranslator.ToWin32(Color.Red));
    IntPtr vPreviouseBrush = SelectObject(vDC, vBrush);