How to check for null in var object

Question

User248267340 posted

I have a var object as follows:

  var files = HttpContext.Request.Form.Files;

In my form, I'm allowing the user to state the local paths of 10 pictures I want uploaded to the form, where

the first 3 paths are set, and the remaining 7 are still null.

This doesn't work:

       if (!string.IsNullOrWhiteSpace(files[4].FileName)) files[4].CopyTo(filestream);

How can I get this right?

Answer 1

User475983607 posted

I do not understand the problem.  It seems you are trying to index into a array and perhaps receiving a index out or rage exception?   It is always best to share the actual exception.

I recommend reading the ASP.NET Core file upload documentation as it illustrates, with source code, how to read multiple files using a foreach loop.

https://docs.microsoft.com/en-us/aspnet/core/mvc/models/file-uploads?view=aspnetcore-2.2

[HttpPost("UploadFiles")]
public async Task<IActionResult> Post(List<IFormFile> files)
{
    long size = files.Sum(f => f.Length);

    // full path to file in temp location
    var filePath = Path.GetTempFileName();

    foreach (var formFile in files)
    {
        if (formFile.Length > 0)
        {
            using (var stream = new FileStream(filePath, FileMode.Create))
            {
                await formFile.CopyToAsync(stream);
            }
        }
    }

    // process uploaded files
    // Don't rely on or trust the FileName property without validation.

    return Ok(new { count = files.Count, size, filePath});
}

Answer 2

User248267340 posted

Thanks so much - the snippet answered all my questions.

I appreciate your insight - I admit that I'm new at this, and am learning from an online website. When I have questions,

it's impossible to get hold of the instructor.

Sorry that I didn't include the error message. But this is great! I'll follow the link as well.

Again, thanks a million!

Corey