Question

Dim hex = "41"
    Dim text As New System.Text.StringBuilder
    For i As Integer = 0 To hex.Length - 2 Step 2
        text.Append(Chr(Convert.ToByte(hex.Substring(i, 2), 16)))
    Next
    System.Diagnostics.Debug.WriteLine(text.ToString)

working perfectly.. System.Diagnostics.Debug.WriteLine writes the output itself in a new line.

 Dim hex = "4100"
    Dim text As New System.Text.StringBuilder
    For i As Integer = 0 To hex.Length - 2 Step 2
        text.Append(Chr(Convert.ToByte(hex.Substring(i, 2), 16)))
    Next
    System.Diagnostics.Debug.WriteLine(text.ToString)

but yet this fails.. (the output isn’t itself in a new line) what’s the explanation for that?

From what I know, doesn’t System.Diagnostics.Debug.Writeline does something which looks like this:

System.Diagnostics.Debug.Write(input)
System.Diagnostics.Debug.Write("\n")

so regardless of my input it should always have a newline char even if there is a terminating 00 char in my input?

Answer 1

Here is the details describing what is going on here:

The string class in .net is an array of char start by pointer to the first char in the array and ends by the special “terminal” char \0.

When you convert the 00 to byte you get 0. but 0 is just equals the terminal char \0

byte b = (byte)`\0`;\\the value of b will be 0

So the Console.Write will ignore all characters after the first \0!. Not only the console will behive this way but also the control components. for instance textBox.Text if you apply a string to it that does have the \0 character, it will not will not display any character after \0 “including the \0 itself”.

Edit:

From what I know, doesn’t System.Diagnostics.Debug.Writeline does something which looks like this:

System.Diagnostics.Debug.Write(input)
System.Diagnostics.Debug.Write("\n")

I guesses that the Debug.WriteLine are not implemented in this way or else we will not notice that behavior. maybe it does concatenate the string with new line like input + "\n".

I can diagnosing the Console.WriteLine using Resharper program. the code is:

[SecuritySafeCritical]
public virtual void WriteLine(string value)
{
    if (value == null)
    {
        this.WriteLine();
    }
    else
    {
        int length = value.Length;
        int num2 = this.CoreNewLine.Length;
        char[] destination = new char[length + num2];
        value.CopyTo(0, destination, 0, length);
        switch (num2)
        {
            case 2:
                destination[length] = this.CoreNewLine[0];
                destination[length + 1] = this.CoreNewLine[1];
                break;

            case 1:
                destination[length] = this.CoreNewLine[0];
                break;

            default:
                Buffer.InternalBlockCopy(this.CoreNewLine, 0, destination, length * 2, num2 * 2);
                break;
        }
        this.Write(destination, 0, length + num2);
    }
}

So it is concatenate the string value with the new line. so it will cause the same effect.