error of "use of unassigned local variable"

[plasmay]

Hi, I am new in learning c#, and have recently encountered a problem:

        static float ComputeAvg(float[] a)
        {
            float sum;
            int i;
            for (i = 0; i <= a.Length; i++)
            {
                sum = sum + a[i];
            }
 
            float avg = sum / (i-1);
 
            return avg;
        }

It comes with a exception says "sum" is "use of unassigned local variable". Since I have already declared "sum" outside the "for" loop, why it says "sum" is unassigned? Thanks!

[tlhintoq]

TIP: When you are writing your question, there is a button on the tool bar that wraps the [code] tags around your copy/pasted code. It helps a bunch. Its the button with a '#' on it. More on tags. They're cool. Check'em out.

Since I have already declared "sum" outside the "for" loop, why it says "sum" is unassigned?

First let me compliment you on your use of 'declared' versus 'assigned'. A lot of people get those mixed up. And your answer is in those two different terms.

You have 'declared' that the variable "sum" exists and that it is a float. But you have not 'assigned' it any value. It is always a good practice to assign a starting value when you create a variable.

float sum = 0.0f;

[plasmay]

Thank you very much. I have found the answer right after I posted my question... Since I know a little about VB, and it will assign an default value for var when I didnt do so, so I was supposed...you know... Anyway, thanks for your reply. have a good night.