I got 2 books about programming in .NET with DirectX, but actually no one of them helped me, cuz the code is written wrong (may be they wrote it for c# 2005). So now i learn the basics from internet. I got stuck on the second tutorial of creating a 2D triangle. I took the code from here and here , combined together and i didnt get errors, but after i run the program, it tells me about the error in one line, that i cant really understand why there is a mistake. As i said, i dont know where the mistake is, so i put here all the code. Sorry for inconveniece.
 namespace Project1
{
    public class CreateDevice: Form
    {
        private Device device = null;
        VertexBuffer vertexBuffer;

        public void OnCreateDevice(object sender, EventArgs e)
        {
            CustomVertex.TransformedColored[ verts = new CustomVertex.TransformedColored[3];
            Device dev = (Device)sender;

            // Now create the vertex buffer
            vertexBuffer = new VertexBuffer(typeof(CustomVertex.TransformedColored), 3, dev, 0,
                                            CustomVertex.TransformedColored.Format, Pool.Default);

            GraphicsStream stm = vertexBuffer.Lock(0, 0, LockFlags.None);            

            verts[0].X = 150; verts[0].Y = 50; verts[0].Z = 0.5f; verts[0].Rhw = 1;
            verts[0].Color = System.Drawing.Color.Aqua.ToArgb();

            verts[1].X = 250; verts[1].Y = 250; verts[1].Z = 0.5f; verts[1].Rhw = 1;
            verts[1].Color = System.Drawing.Color.Brown.ToArgb();

            verts[2].X = 50; verts[2].Y = 250; verts[2].Z = 0.5f; verts[2].Rhw = 1;
            verts[2].Color = System.Drawing.Color.LightPink.ToArgb();

            stm.Write(verts);
            vertexBuffer.Unlock();          

        }


        public CreateDevice()
        {
            this.ClientSize = new System.Drawing.Size(400,300);
            this.Text = "D3D Tutorial 01: CreateDevice";            
        }

        public bool InitializeGraphics()
        {
        try
        {
           // Now  setup our D3D stuff
           PresentParameters presentParams = new PresentParameters();
           presentParams.Windowed=true;
           presentParams.SwapEffect = SwapEffect.Discard;
           device = new Device(0, DeviceType.Hardware, this,
                       CreateFlags.SoftwareVertexProcessing, presentParams);
           return true;
        }
       catch (DirectXException)
        {
         return false;
        }
        }

        static void Main()
        {

            using (CreateDevice frm = new CreateDevice())
            {
            if (!frm.InitializeGraphics()) // Initialize Direct3D
            {
                MessageBox.Show("Could not initialize Direct3D.  This tutorial will exit.");
                return;
            }
            frm.Show();
            while(frm.Created)
            {
                frm.Render();
                Application.DoEvents();
            }
            }
        }

        public void Render()
            {
            if (device == null)
                return;

            device.Clear(ClearFlags.Target, System.Drawing.Color.Blue, 1.0f, 0);
            device.BeginScene();    

            device.SetStreamSource(0, vertexBuffer, 0);
            device.VertexFormat = CustomVertex.TransformedColored.Format;
            device.DrawPrimitives(PrimitiveType.TriangleList, 0, 1);   - Here the error is

            device.EndScene();
            device.Present();
            }
    }

}

Another error you are having is in this line

which should be

CustomVertex.TransformedColored verts = new CustomVertex.TransformedColored[3];

MJP:

What is the error it gives you?

EDIT:  Does your OnCreateDevice handler ever get called? 

The error is

 Unhandled Exception: Error in the application.
-2005530516 (D3DERR_INVALIDCALL)
   at Microsoft.DirectX.Direct3D.Device.DrawPr
pe, Int32 startVertex, Int32 primitiveCount)

 hm...i dont really think it gets called. Where do i call it? In static void Main?

NightCreature:

The last value in SetStreamSource cannot be 0, you have to tell it how big a vertex actually is, so that should actually be CustomVertex.TransformedColored.StrideSize.

Another error you are having is in this line

CustomVertex.TransformedColored[ verts = new CustomVertex.TransformedColored[3];

which should be

CustomVertex.TransformedColored verts = new CustomVertex.TransformedColored[3];

 I fixed the first one, but it still doesnt work :(

The second one is just a problem of copy-paste.

This error means that on the point where you call drawPrimitive is not allowed to be called, are you sure you are creating a valid device and storing that in the class. I am not a managed DX coder I use the unmanaged version and it's a wee bit different in how to create a device. So I can't help you in that respect.

NightCreature:

Unhandled Exception: Error in the application.
-2005530516 (D3DERR_INVALIDCALL)
   at Microsoft.DirectX.Direct3D.Device.DrawPr
pe, Int32 startVertex, Int32 primitiveCount)

This error means that on the point where you call drawPrimitive is not allowed to be called, are you sure you are creating a valid device and storing that in the class. I am not a managed DX coder I use the unmanaged version and it's a wee bit different in how to create a device. So I can't help you in that respect..

 I'm not sure it's valid device, i'm not sure all i've done is right :)) Is unmanaged version more comfortable? What are the differences?

Bad Habit:

I can't see where OnCreateDevice() gets called. Call it right after you create the device, also make sure you subscribe it to the device's event handler so it gets called whenever the device is reset.

If you're comfortable with C++ then that's the way to go. Managed DX is dead now, C++ killed it off years ago. If you want to stick with C# then try SlimDX or XNA games studio.

 How do i call it? I put it right after i created device, here:

        try
        {
           // Now  setup our D3D stuff
           PresentParameters presentParams = new PresentParameters();
           presentParams.Windowed=true;
           presentParams.SwapEffect = SwapEffect.Discard;
           device = new Device(0, DeviceType.Hardware, this,
                       CreateFlags.SoftwareVertexProcessing, presentParams);
           OnCreateDevice();
           return true;
        }

 but what arguments do i tell him?

So you advice me to learn C++ if i wanna use direct3D? I'm usual to c# and dont wanna swap to another language :( Do you have some online conversation accounts, like icq or skype?