CODEWITHSUNDEEP
c#variables
user3215251
user3215251

Reputation: 249

Using variables only assigned in if statements

I am using C# with VS2013 and .Net 4.5.2.

I create a variable, assign it a value if a certain other variable is a boolean set to true. Using the same variable later, to see if I should process anything involving that variable.

FileInfo newFile;
ExcelPackage assetTemplate;
ExcelWorksheet assetWorkbook;

if (load.assetDelivery) // Bool in another class
{
   newFile = new FileInfo(load.assetDeliveryTemplate);
   assetTemplate = new ExcelPackage(newFile);
   assetWorkbook = assetTemplate.Workbook.Worksheets[1];
}

// In this function later on, assetWorkbook and assetTemplate are causing errors
// Error    1   Use of unassigned local variable 'assetWorkbook'    
if (load.assetDelivery)
{
   assetWorkbook.Cells.AutoFitColumns();
   destination = load.exportFileDestination + load.assetDeliveryName +              DateTime.Now.ToString("yyyyMMddHHmmss") + ".xlsx";
   assetTemplate.SaveAs(new FileInfo(destination));
}

Upvotes: 0

Views: 97

Answers (5)

Selman Genç
Selman Genç

Reputation: 101681

Assign null to your variables:

ExcelPackage assetTemplate = null;
ExcelWorksheet assetWorkbook = null;

Upvotes: 2

Jeff Watkins
Jeff Watkins

Reputation: 6359

You can use defaults (c.f. the other answers), but this looks like an example of some missing functional composition. If you had a function that looked something like

public void CreateSheet(string exportDestination, string assetName) 
{
    FileInfo newFile = new FileInfo(load.assetDeliveryTemplate);
    ExcelPackage assetTemplate = new ExcelPackage(newFile);
    ExcelWorksheet assetWorkbook = assetTemplate.Workbook.Worksheets[1];

    assetWorkbook.Cells.AutoFitColumns();
    destination = exportDestination + assetName + DateTime.Now.ToString("yyyyMMddHHmmss") + ".xlsx";
    assetTemplate.SaveAs(new FileInfo(destination));

}

It would always be safe.

Upvotes: 0

Habib
Habib

Reputation: 223207

Compiler is complaining because there is no way for it to know that control flow will enter the check (true part) and your fields/variables will be definitely assigned. Hence the error.

You can fix that by either assigning those fields default values, 

ExcelPackage assetTemplate = default(ExcelPackage);
ExcelWorksheet assetWorkbook = default(ExcelWorksheet);

or by specifying an else part:

if (load.assetDelivery) // Bool in another class
{
   newFile = new FileInfo(load.assetDeliveryTemplate);
   assetTemplate = new ExcelPackage(newFile);
   assetWorkbook = assetTemplate.Workbook.Worksheets[1];
}
else
{
    ExcelPackage assetTemplate = default(ExcelPackage);
    ExcelWorksheet assetWorkbook = default(ExcelWorksheet);
}

See: 5.3 Definite assignment - MSDN

Upvotes: 2

Joe Enos
Joe Enos

Reputation: 40393

In C#, you must guarantee that you initialize a local variable prior to using it. In this scenario, assetWorkbook will never be assigned a value if your first if fails, which means the compiler can't guarantee that it was ever initialized prior to use.

If you give them an initial value, even null, then your code will compile - just remember that if the value is null, then you're subject to a NullReferenceException if it never gets a real value, so make sure you either do a null check first, or are 100% sure you gave it a value.

Upvotes: 0

Amit Joki
Amit Joki

Reputation: 59232

Just initialize it with default value.

ExcelWorksheet assetWorkbook = default(ExcelWorksheet);

Upvotes: 0

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