Question

public class Form1 : System.Windows.Forms.Form
{
    private void eachCornerPix (object sender, PaintEventArgs e, out float Wx, out float Wy, out float Vx, out float Vy)
    {
        Graphics g = this.CreateGraphics();
        Pen penBlu = new Pen(Color.Blue, 2);
        SolidBrush redBrush = new SolidBrush(Color.Red);
        int width = 2;    // 1 pixel wide in x
        int height = 2;
        float [] Wxc = {0.100f, 5.900f, 5.900f, 0.100f}; 
        float [] Wyc = {0.100f, 0.100f, 3.900f, 3.900f}; 
        for (int i = 0; i<3; i++)
        {
            Wx = Wxc[i];
            Wy = Wyc[i];
            Vx = ((Wx - WXmin)*((VXmax-VXmin)+VXmin)/(WXmax-WXmin));  
    Vy = ((Wy - WYmin)*(VYmax-VYmin)/(WYmax-WYmin)+VYmin); 
    Console.WriteLine("eachCornerPix Vx= {0}", Vx);
    Console.WriteLine("eachCornerPix Vy= {0}", Vy);
    g.FillRectangle(redBrush, Vx, Vy, width, height);
            g.Dispose();
        }
    }
}

Desired effect: Use the array values (Wxc, Wyc) and re-assign them to Wx and Wy. Then use
Wx and Wy as components to calculate Vx and Vy.
My end goal…once compile issues are resolved, is to pass each array value listed
using this method. This should allow 4 xy point pairs to be plotted.

Errors:

pass1.cs(51,18): error CS0177: The out parameter 'Wx' must be assigned to before control leaves the current method
pass1.cs(51,18): error CS0177: The out parameter 'Wy' must be assigned to before control leaves the current method
pass1.cs(51,18): error CS0177: The out parameter 'Vx' must be assigned to before control leaves the current method
pass1.cs(51,18): error CS0177: The out parameter 'Vy' must be assigned to before control leaves the current method

Answer 1

Put this at the beginning of your method:

Wx = 0f;
Wy = 0f;
Vx = 0f;
Vy = 0f;