I'm developing a website in Asp.Net and one of the page requires users to upload files. The client wants the file size limit to be set to 5MB max. I have set the limit in the `web.config` using the following code; 

```
 <system.webServer>
<security>
  <requestFiltering>
    <requestLimits maxAllowedContentLength="5242880" /> <!--5MB-->
  </requestFiltering>
</security> </system.webServer>

```

The C# code for the page to check the file extension and display the error message to the users has the following code.

```
string[] validFileTypes = { "doc", "docx", "xls", "pdf" };
    string ext = System.IO.Path.GetExtension(FileUpload1.PostedFile.FileName);
    bool isValidFile = false;

    for (int i = 0; i < validFileTypes.Length; i++)
    {
        if (ext == "." + validFileTypes[i])
        {
            isValidFile = true;
            break;
        }
    }
        if (!isValidFile)
        {
            DisplayMessage.Visible = true;
            DisplayMessage.Text = "Invalid file or file size has exceeded it max limit of 5MB. Please upload a file with one of the following extension; <br /><br />" +
            string.Join(", ", validFileTypes) + "or a smaller file";
    }
    else
    {
        string targetFolder = HttpContext.Current.Server.MapPath("~/App_Data/");
        string targetPath = Path.Combine(targetFolder, FileUpload1.FileName);
        FileUpload1.SaveAs(targetPath);

        DisplayMessage.Visible = true;
        DisplayMessage.Text = "File uploaded successfully.";
    }

```

The issue I am having is when I try to upload a file which is bigger than 5MB instead of the page displaying the error message it throws me a `stack trace` ![enter image description here](https://i.stack.imgur.com/xKv71.png) 

Can someone please tell me where I'm going wrong. Many Thanks in advance!