RadUpload ChunkTag or How To Deal With Uploaded Files by Chunk

Telerik RadUpload for Silverlight supports Chunk tagging. Thus, the RadUploadHandler has the ability to tag the uploaded chain of chunks. For example, you can use the ChunkTag to save the uploaded files in a database by chunk and not wait for the whole file to be uploaded (and saved to disk by default).

Chunk-Tag rely on two properties in the RadUploadHandler class:

  • FormChunkTag: The ChunkTag value supplied by the upload client for the current chunk.
  • ResultChunkTag: Gets or sets the ChunkTag value returned from the upload-handler to the upload-client.

InitializeChunkStorage and SaveChunkData are two main methods you should be aware of when you customize your upload handler.

The following example demonstrate how you can create custom class and override the InitializeChunkStorage and SaveChunkData methods.

public class SampleUploadHandler : RadUploadHandler 
    int FileID = 0; 
    public override bool InitializeChunkStorage(string filePath) 
        // If this is the first time the InitializeChunkStorage is invoked, 
        // create the a new Key (just a time stamp in our example). 
        // The next time InitializeChunkStorage gets invoked, we will use this Key. 
        if (this.IsNewFileRequest()) 
            this.ResultChunkTag = MyUniqueKeyGenerator.GetKey(); 
            if (this.FormChunkTag != null) 
                this.ResultChunkTag = this.FormChunkTag; 
        return true; 
    public override bool SaveChunkData(string filePath, long position, byte[] buffer, int contentLength, out int savedBytes) 
        savedBytes = 0; 
        bool success = false; 
        string UserID = this.GetQueryParameter("UserID"); 
        string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["FilesDataBaseConnectionString"].ConnectionString; 
        using (SqlConnection conn = new SqlConnection(connectionString)) 
            string cmdText = "INSERT INTO FileChunk(FileChunk, ChunkTag, ChunkSize, UserID) VALUES(@FileChunk, @ChunkTag, @ChunkSize, @UserID)  SET @Identity = SCOPE_IDENTITY()"; 
            SqlCommand cmd = new SqlCommand(cmdText, conn); 
            SqlParameter identityParam = new SqlParameter("@Identity", SqlDbType.Int, 0, "FileID"); 
            identityParam.Direction = ParameterDirection.Output; 
            cmd.Parameters.AddWithValue("FileChunk", buffer); 
            cmd.Parameters.AddWithValue("ChunkSize", buffer.Length); 
            cmd.Parameters.AddWithValue("ChunkTag", this.ResultChunkTag); 
            cmd.Parameters.AddWithValue("UserID", UserID); 
            FileID = (int)identityParam.Value; 
        // Note: do not forget to set the success value: 
        success = true; 
        if (!success) 
            string fileName = this.GetFileName(); 
            this.AddReturnParam(RadUploadConstants.ParamNameMessage, String.Format("Cannot save the file: [{0}]", fileName)); 
        return success; 
    public override Dictionary<string, object> GetAssociatedData() 
        Dictionary<string, object> associatedData = base.GetAssociatedData(); 
        if (this.IsFinalFileRequest()) 
            associatedData.Add("FileID", FileID.ToString()); 
        return associatedData; 
    public class MyUniqueKeyGenerator 
        public static string GetKey() 
            // Here you should create an appropriate Key depending on your scenario. 
            // For example it may be a real GUID or UserID-related... 
            string key = string.Format(".{0:yyyymmdd.hhmmss}", DateTime.Now); 
            return key; 
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