Another way to pass data into a thread

In the previous thread post I showed a way you can pass information into a thread. Here is another way in which you instantiate the class containing the method you want your thread to call first.

Math math = new Math();
math.Value1 = 1;
math.Value2 = 3;

ThreadPool.QueueUserWorkItem(math.Add);

Now when math.Add is called, it has all the information it needs to do its work.

Easiest way to start a thread

The easiest way to start a process on another thread is to call ThreadPool.QueueUserWorkItem.
Example:

// DoSomeWork is a method.
ThreadPool.QueueUserWorkItem(DoSomeWork);

Note: The DoSomeWork method has to have an Object as a parameter.

private static void DoSomeWork(object info)
{
    // Code that does work.
}

If you need to pass data into your method, you can do so:

ThreadPool.QueueUserWorkItem(DoSomeWork, "Info")

You will just have to cast the object back into the appropriate data type.

private static void DoSomeWork(object info)
{
    string workInfo = (string) info;
    // Code that does work.
}

More Info: MSDN: QueueUserWorkItem

Adding Text to Images

Adding text to an image requires 2 steps:

• Create a Graphics object
• Create a Font object
• Call Graphics.DrawString method

Code Example:

private void Form1_Paint(object sender, PaintEventArgs e)
{
    Graphics g = e.Graphics;
    Font f = new Font("Arial", 12, FontStyle.Bold);
    g.DrawString("Copyright 2009", f, Brushes.Black, 10, 10);
}

Why would you do this?
Most likely you wouldn't. You would use a label instead. But you can also draw strings on images and that is most likely what you would use this method for.

More Info: MSDN: Graphics.DrawString Method

Assigning Images to Windows Controls

Use a Bitmap or Image class.

button1.BackgroundImage = new Bitmap("bm.jpg");
// or
pictureBox1.BackgroundImage = Image.FromFile("bm.jpg");

More Info: MSDN: Image Class

Creating and Saving a Picture

There are 3 steps to creating and saving a picture:

1. Create a Bitmap object.
2. Edit it using Graphics object.
3. Call Bitmap.Save method to save it.

Code Example:

Bitmap bm = new Bitmap(100, 100);
Graphics g = Graphics.FromImage(bm);
g.DrawEllipse(new Pen(Color.Red), new Rectangle(5, 5, 90, 90));
bm.Save("bm.jpg", ImageFormat.Jpeg);

Here is what it looks like:
If you would like to edit an existing image instead, you can use:

Bitmap bm = new Bitmap("existingImage.jpg");

More Info: MSDN: Bitmap Class

Nullable

When declaring a value type (int, bool, char, DateTime, etc.) you cannot initialize it to null or you'll get this error message: To fix this you need to declare your variable as nullable:

Nullable<bool> answer1 = null;
// or
bool? answer2 = null;

When this is done, 2 new properties become available to you, HasValue and Value. Now you can check if your variable has been assigned a value yet or if it's still null with HasValue.

if (answer1.HasValue) Console.WriteLine("answer1 is {0}", answer1);

More Info: MSDN: Nullable(T) Structure

Authenticated User Information

So you have used the built-in ASP.NET Login controls (Login, LoginView, etc). Now what if you want to get at the authenticated user information in code?

Access it through the HttpContext.Current.User property.

Examples:

// Get the user's name
string userName = HttpContext.Current.User.Identity.Name;

More Info: MSDN: HttpContext.Current.User