How to handle NullReferenceExceptions without using try/catch

Question

I have a code like this:

string fileLocation = Request.Form["FileName"].ToString(); 

if (!string.IsNullOrEmpty(fileLocation))
{                          
    var deleteFile = fileLocation.Split('\\')[1];
    var pathe = Path.Combine(uploadPath, deleteFile;
    if (System.IO.File.Exists(pathFile))
    {
        System.IO.File.Delete(pathFile);
    }
}

Usually if i don't select a file, Request.Form["FileName"].ToString() will return a SystemNullException which I intend to set it as null.

Is there anyway i can do it without using try catch?

something like `string fileLocation = Request?.Form["FileName"]?.ToString();` — Dmitry Bychenko, Jul 03 '18 at 09:35
Some part of `Request.Form["FileName"].ToString()` will be null. Find out which bit by adding a breakpoint and generating the condition, then put in a specific check, e.g., `if (Request != null)`, or `if (Request.Form["FileName"] != null)` before the `.ToString()` call. — Ian, Jul 03 '18 at 09:39

score 3 · Answer 1 · edited Jul 03 '18 at 09:41

3

If Request.Form["FileName"] returns null then you can't do .ToString().

So you can use null propagator to get around this:

Request.Form["FileName"]?.ToString()

edited Jul 03 '18 at 09:41

Uwe Keim

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answered Jul 03 '18 at 09:39

Ross Miller

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score 1 · Answer 2 · edited Jul 03 '18 at 09:41

1

Just check before applying .ToString.

var result = Request.Form["FileName"];
if(result != null)
{
    string fileLocation = result.ToString();
    if (!string.IsNullOrEmpty(fileLocation))
    {
        var deleteFile = fileLocation.Split('\\')[1];
        var pathe = Path.Combine(uploadPath, deleteFile;
        if (System.IO.File.Exists(pathFile))
        {
            System.IO.File.Delete(pathFile);
        }
    }
}

edited Jul 03 '18 at 09:41

Uwe Keim

39,551
56
175
291

answered Jul 03 '18 at 09:39

Amit Kumar

5,888
11
47
85

2

Would prefer if(result == null) return to reduce indentation. Or use null propagtor – Ross Miller Jul 03 '18 at 09:41

How to handle NullReferenceExceptions without using try/catch

2 Answers2