Problem with unassigned local variable in c#

Question

Ok, i feel so ashamed to ask this question, but I can't understand why this code in c# does not compile in vs2010 express:

string[] value;
for (int i = 0; i < 3; i++)
        {
            value[i] = "";
        }

Why it says that it's unassigned?

Chris Ballard · Accepted Answer · 2011-04-03 15:57:23Z

5

you need to assign the array first, then items in the array.

 string[] value = new string[3];

If you want to add items dynamically, and have it resize as needed, you might be better off with a generic list, eg.

var values = new List<string>();
for(int i = 0; i < 3; i++)
{
    values.Add("");   // or values.Add(String.Empty);
}

answered Apr 3, 2011 at 15:57

Chris Ballard

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1 Comment

Magnetic_dud Over a year ago

Thanks! I forgot how to do it :(

NightDweller · Accepted Answer · 2011-04-03 16:01:14Z

2

Chris's already answered, and i'd like to add that you'd typically want to do the following:

string[] value = new string[3];
for (int i=0; i<value.Length; i++)
{
   value[i]="";
}

answered Apr 3, 2011 at 16:01

NightDweller

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2 Comments

Magnetic_dud Over a year ago

+1! Thanks also! Actually I do this: string[] value = new string[maxarray]; for (int i = 0; i < maxarray; i++)

Grizzly Over a year ago

To elaborate why this should be done: 1) using value.Length is clearer then some hardcoded value (or another variable which should hold the length (but might not at a later time due to code changes). 2) I'm not sure if that's still the case, but last time I checked the JIT was much better optimizing this code when the variable is checked against value.Length instead of some other argument. This is/was because this was recognized as a pattern where the variable couldn't be out of range for the array, so the array accesses need no range checking.

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