Use of unassigned local variable please

Question

I created much for loops and want to put value from a int to a string.

String strasze = dataGridView1.Rows[rows].Cells[straszeint].Value.ToString();
String stadt = dataGridView1.Rows[rows].Cells[stadtint].Value.ToString();
land = dataGridView1.Rows[rows].Cells[landint].Value.ToString();

hersteller = dataGridView1.Rows[rows].Cells[colIndex].Value.ToString();
kundennummer = dataGridView1.Rows[rows].Cells[kundennummerint].Value.ToString();
haendler = dataGridView1.Rows[rows].Cells[haendlerint].Value.ToString();

Here is a example for loop:

int landint;

for (int i = 0; i < datagridview.Columns.Count; i++)
{
    if (datagridview.Columns[i].Name.Equals(landname))
    {
        landint = i;
        break;
    }
}

What is wrong? It shows me the error on straszeint, stadtint, landint

//EDIT

int straszeint;

for (int i = 0; i < datagridview.Columns.Count; i++)
{
    if (datagridview.Columns[i].Name.Equals(straszennamen))
    {
        straszeint = i;
        break;
    }
}

You may have already looked at the marked duplicate, but it seems you didn't fully understand the information there. It directly addresses this issue of a variable being "not definitely assigned", as in your code. — Peter Duniho, Aug 11 '16 at 07:42

score 1 · Answer 1 · answered Aug 11 '16 at 07:03

From your code, it is possible straszeint is never assigned a value. Assume what happens if datagridview.Columns.Count is 0, or there is no column matching the name. Then straszeint is never set to a value.

The compiler doesn't know what you know, so it just checks all paths and sees if there is a possible problem with an unset variable.

The easiest thing to do here is to set the variable to some arbitrary number and check that later:

int straszeint = -1;

for (int i = 0; i < datagridview.Columns.Count; i++)
    ...

if (straszeint == -1)
{
    throw new Exception("Column 'straszennamen' could not be found!");
}

sujith karivelil · Accepted Answer · 2016-08-11T07:20:42.177

0

This is because Compiler is smarter than a developer

You should Initialize the local variables before accessing their values, In your case there may be changes for skipping the iteration of the loop, or the condition inside the loop will evaluate to false in all iteration. and you are using the value (say straszeint) after the iterations.

Compiler expecting such situations that's why it showing such errors.

You can simply solve this by initializing the variable either with 0 or any other value that's up to you.

int straszeint=-1;

for (int i = 0; i < datagridview.Columns.Count; i++)
{
   if (datagridview.Columns[i].Name.Equals(straszennamen))
   {
     // Let it is false for all iterations
     straszeint = i;
     break;
   }
}
// straszeint will be -1 here if the condition is false for all iteration
if(straszeint!=-1)
{
   //Proceed with the action
}

Updates : Why should we initialize with -1 instead for 0

The .Cells will follows the 0 based indexing, So it will give the First cell value even if the condition evaluates to false.

edited Aug 11 '16 at 07:20

answered Aug 11 '16 at 07:05

sujith karivelil

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Thanks! Works perfectly! – Gomze Aug 11 '16 at 07:06
"straszeint will be zero here if the condition is false for all iteration" Wrong. It could also be the first column... – Patrick Hofman Aug 11 '16 at 07:10
This is because int32 is not a nullable type right? – downrep_nation Aug 11 '16 at 07:13
@PatrickHofman : Well, I agree with your point. But there is nothing wrong with that sentence. the value of `straszeint` will be `0` there, hence `strasze` will be the value in the first cell. Hope that I'm right. – sujith karivelil Aug 11 '16 at 07:16
@downrep_nation, no because it is not initialized. Method variables have to be initialized. This would be true for an object too. – Patrick Hofman Aug 11 '16 at 07:24
@PatrickHofman thanks for the explanation – downrep_nation Aug 11 '16 at 07:30

Use of unassigned local variable please

2 Answers2