Question

I want to create a class library which is able to draw pie or bar chart.
i’m using following codes…

Graphics g = CreateGraphics();

when i used that code visual studio told me you cant use with dll files(Class Library).

i’ve still problem how can i fix that… o_O

asking more information:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Data;


namespace KouChart
{
    public class Pasta
    {
        public void PastaCiz(int a, int b, int c)
        {
            float toplam = a + b + c;
            float deg1 = (a / toplam) * 360;
            float deg2 = (b / toplam) * 360;
            float deg3 = (c / toplam) * 360;
            Pen p = new Pen(Color.Red, 2);
            Graphics g = this.CreateGraphics();
            Rectangle rec = new Rectangle(50, 12, 150, 150);
            Brush b1 = new SolidBrush(Color.Red);
            Brush b2 = new SolidBrush(Color.Black);
            Brush b3 = new SolidBrush(Color.Blue);
            Brush b4 = new SolidBrush(Color.Yellow);

            g.DrawPie(p, rec, 0, deg1);
            g.FillPie(b1, rec, 0, deg1);
            g.DrawPie(p, rec, deg1, deg2);
            g.FillPie(b2, rec, deg1, deg2);
            g.DrawPie(p, rec, deg2 + deg1, deg3);
            g.FillPie(b3, rec, deg2 + deg1, deg3);
        }
    }
}

and errors: Error 1 ‘KouChart.Pasta’ does not contain a definition for ‘CreateGraphics’ and no extension method ‘CreateGraphics’ accepting a first argument of type ‘KouChart.Pasta’ could be found (are you missing a using directive or an assembly reference?) C:\Users\Muyu\Documents\Visual Studio 2010\Projects\KouChart\KouChart\Pasta.cs 20 31 KouChart

Answer 1

The CreateGraphics() method belongs to the Control class. If Pasta is supposed to be a control, then you should derive it from Control.

i.e.

public class Pasta : Control
{
    public void PastaCiz(int a, int b, int c)          
    { ... }
}

By the way, if you are writing a control, you would want to draw it in the OnPaint() method, and you don’t need to call CreateGraphics() because one is already created for you. Here’s a very quick example to illustrate, but I’m not a control developer so please don’t consider this to be the correct approach.

public class Pasta : Control
{
    int a;
    int b;
    int c;

    public void PastaCiz(int a, int b, int c)
    {
        this.a = a;
        this.b = b;
        this.c = c;
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);
        float toplam = a + b + c;
        float deg1 = (a / toplam) * 360;
        float deg2 = (b / toplam) * 360;
        float deg3 = (c / toplam) * 360;
        Pen p = new Pen(Color.Red, 2);
        Graphics g = e.Graphics;                           <-- note
        Rectangle rec = new Rectangle(50, 12, 150, 150);
        Brush b1 = new SolidBrush(Color.Red);
        Brush b2 = new SolidBrush(Color.Black);
        Brush b3 = new SolidBrush(Color.Blue);
        Brush b4 = new SolidBrush(Color.Yellow);
        g.DrawPie(p, rec, 0, deg1);
        g.FillPie(b1, rec, 0, deg1);
        g.DrawPie(p, rec, deg1, deg2);
        g.FillPie(b2, rec, deg1, deg2);
        g.DrawPie(p, rec, deg2 + deg1, deg3);
        g.FillPie(b3, rec, deg2 + deg1, deg3);
    }
}

Also note that it would be more efficient to cache those Pen and Brush instances instead of recreating them every time.