A simple question of methods

Terry Bockman

Hi all,

I am teaching myself C#, and have a simple problem. The compiler displays an error message for the code (below). I have spent hours trying to figure out why it won't compile, and, hope one of you very knowledgeable programmers will tell me what is wrong.

Thank-you in advance, Terry

--------------SOURCE CODE & COMPILER ERROR BELOW----------------

// Line 4

using System;

public class a_String
{
     public static void Main()
    {
      string aString;
      string strAdded;
      string firstStr = "ABC";
// L15
      Console.Out.Write("Enter the letter after " + firstStr);
      aString = letter(strAdded);
      Console.Out.WriteLine("You entered the letter " + aString);

// L20

} // end Main

// L24
      public static string letter(string input)
     {
        string theLetter;
        theLetter = Console.ReadLine();
        return theLetter;
     }
} // end class a_String
// L32

// ----- COMPILER ERRORS -----
// PassStr.cs(17,24): error CS0165: Use of unassigned local variable 'strAdded'

4 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes14y ago
Accepted answer
Unlike many other programming languages, local variables in C# don't have a default value and must therefore be given a value before they are used.

In particular, if you pass a local variable as an argument to a method, you must give it a value first. The only exceptions to this are 'out' parameters - something which you might not have come across yet.

So, when the C# compiler sees you passing strAdded to the letter method, it complains that it's 'unassigned'.

Bala's solution deals with that problem by assigning an empty string to it. It doesn't actually matter (but does no harm) if you assign a value to aString or not because the compiler can see that it's being assigned a value a few lines down before you use it.

However, one other thing I've noticed is that you don't actually use the 'input' parameter in the letter method anyway and could therefore get rid of the strAdded variable altogether:

using System;

public class a_String
{
public static void Main()
{
string aString;
string firstStr = "ABC";

Console.Out.Write("Enter the letter after " + firstStr);
aString = letter();
Console.Out.WriteLine("You entered the letter " + aString);

} // end Main

public static string letter()
{
string theLetter;
theLetter = Console.ReadLine();
return theLetter;
}
} // end class a_String
Terry Bockman14y ago
That is good info! It helps explain a lot.

Thank-you!
Terry :)
Terry Bockman14y ago
Sorry to get back to you so late; been on vacation.
I tried your correction and it works!

Thanks for the help, Terry
Marish Balasubramanian14y ago
change the declaration as follows

string aString="";
string strAdded="";