DevExtreme React - Server-Side Implementation in ASP.NET

[HttpPost]
// "file" is the value of the FileUploader's "name" option
public ActionResult AsyncUpload(HttpPostedFileBase file)
{
    // Specifies the target location for the uploaded files
    string targetLocation = Server.MapPath("~/Files/");

    // Specifies the maximum size allowed for the uploaded files (700 kb)
    int maxFileSize = 1024 * 700;

    // Checks whether or not the request contains a file and if this file is empty or not
    if (file == null || file.ContentLength <= 0) {
        throw new HttpException("File is not specified");
    }

    // Checks that the file size does not exceed the allowed size
    if (file.ContentLength > maxFileSize) {
        throw new HttpException("File is too big");
    }

    // Checks that the file is an image
    if (!file.ContentType.Contains("image")) {
        throw new HttpException("Invalid file type");
    }

    try {
        string path = System.IO.Path.Combine(targetLocation, file.FileName);
        // Here, make sure that the file will be saved to the required directory.
        // Also, ensure that the client has not uploaded files with malicious content.
        // If all checks are passed, save the file.
            file.SaveAs(path);
    }
    catch (Exception e) {
        throw new HttpException("Invalid file name");
    }
    return new EmptyResult();
}

<HttpPost>
'  "file" is the value of the FileUploader's "name" option
Function AsyncUpload(file As HttpPostedFileBase) As ActionResult
    ' Specifies the target location for the uploaded files'
    Dim targetLocation As String = Server.MapPath("~/Files/")

    ' Specifies the maximum size allowed for the uploaded files (700 kb)'
    Dim maxFileSize As Integer = 1024 * 700

    ' Checks whether or not the request contains a file and if this file is empty or not'
    If (IsNothing(file) Or file.ContentLength <= 0) Then
        Throw New HttpException("File is not specified")
    End If

    ' Checks that the file size does not exceed the allowed size'
    If (file.ContentLength > maxFileSize) Then
        Throw New HttpException("File is too big")
    End If

    ' Checks that the file is an image'
    If (Not file.ContentType.Contains("image")) Then
        Throw New HttpException("Invalid file type")
    End If

    Try
        Dim path As String = System.IO.Path.Combine(targetLocation, file.FileName)
        ' Here, make sure that the file will be saved to the required directory.'
        ' Also, ensure that the client has not uploaded files with malicious content.'
        ' If all checks are passed, save the file.'
            file.SaveAs(path)
    Catch ex As Exception
        Throw New HttpException("Invalid file name")
    End Try

    Return New EmptyResult()

End Function

[NonAction]
protected override void OnActionExecuted(ActionExecutedContext filter) {
    var exception = filter.Exception;
    if (exception != null) {
        filter.HttpContext.Response.StatusCode = 500;
        filter.Result = new JsonResult {
            Data = exception.Message
        };
        filter.ExceptionHandled = true;
    }
}

<NonAction()>
Protected Overrides Sub OnActionExecuted(ByVal filter As ActionExecutedContext)
    Dim exception As Exception = filter.Exception
    If exception IsNot Nothing Then
        filter.HttpContext.Response.StatusCode = 500
        filter.Result = New JsonResult With {.Data = exception.Message}
        filter.ExceptionHandled = True
    End If
End Sub

public ActionResult SyncUpload() {

    // Specifies the target location for the uploaded files
    string targetLocation = Server.MapPath("~/Files/");

    // Specifies the maximum size allowed for the uploaded files (700 kb)
    int maxFileSize = 1024 * 700;

    // Checks whether the request contains any files
    if(Request.Files.Count == 0)
        return View("Index");

    HttpFileCollectionBase files = Request.Files;
    for (int index = 0; index < files.Count; index++ ) {
        HttpPostedFileBase file = files[index];

        // Checks that the file is not empty
        if (file.ContentLength <= 0)
            continue;
        string fileName = file.FileName;

        // Checks that the file size does not exceed the allowed size
        if (file.ContentLength > maxFileSize)
            continue;

        // Checks that the file is an image
        if (!file.ContentType.Contains("image"))
            continue;

        try {
            string path = System.IO.Path.Combine(targetLocation, file.FileName);
            // Here, make sure that the file will be saved to the required directory.
            // Also, ensure that the client has not uploaded files with malicious content.
            // If all checks are passed, save the file.
                file.SaveAs(path);
        }
        catch (Exception e) {
            continue;
        }
    }
    return View("Index");
}

Function SyncUpload() As ActionResult
    ' Specifies the target location for the uploaded files'
    Dim targetLocation As String = Server.MapPath("~/Files/")

    ' Specifies the maximum size allowed for the uploaded files (700 kb)'
    Dim maxFileSize As Integer = 1024 * 700

    Dim files As HttpFileCollectionBase = Request.Files

    ' Checks whether the request contains any files'
    If files.Count = 0 Then
        Return View("Index")
    End If

    For i = 0 To files.Count - 1
        Dim file As HttpPostedFileBase = files(i)

        ' Checks that the file is not empty'
        If (file.ContentLength <= 0) Then
            Continue For
        End If

        Dim fileName As String = file.FileName

        ' Checks that the file size does not exceed the allowed size'
        If (file.ContentLength > maxFileSize) Then
            Continue For
        End If

        ' Checks that the file is an image'
        If (Not file.ContentType.Contains("image")) Then
            Continue For
        End If

        Try
            Dim path As String = System.IO.Path.Combine(targetLocation, file.FileName)
            ' Here, make sure that the file will be saved to the required directory.'
            ' Also, ensure that the client has not uploaded files with malicious content.'
            ' If all checks are passed, save the file.'
                file.SaveAs(path)
        Catch ex As Exception
            Continue For
        End Try
    Next i

    Return View("Index")
End Function