How to – Upload File to File Column using InitializeFileBlocksUpload and UploadBlock Request (Dynamics 365/ CRM)

Sharing a sample code, we can use to upload a file to the File Column

Also read –

File Attribute

Here we would upload the below file to one of the contact records.

For file size more than 4 MB we need to implement chunking and combine the data before committing.


On calling the method –

We can see the file uploaded to the contact record.

The restriction of using chunked upload for files greater than 16 MB has been removed, see the below code for full file upload. The chunking APIs are still kept for backward compatibility.

Example – .NET C# code for full file upload. (recommended way of uploading)

Hope it helps..

  private static void UploadFile(CrmServiceClient svc, string entityName, Guid recordGuid,
           string fileAttributeName, string filePath, string fileName)
            // get the file content in byte array
            var fileContentByteArray = File.ReadAllBytes(filePath);

            var initializeFileBlocksUploadRequest = new InitializeFileBlocksUploadRequest()
                Target = new EntityReference(entityName, recordGuid),
                FileAttributeName = fileAttributeName,
                FileName = fileName

            var initializeFileBlocksUploadResponse = (InitializeFileBlocksUploadResponse)

            // to store different block id in case of chunking           
            var lstBlock = new List<string>();         

            // 4194304 = 4 MB
            for (int i = 0; i < fileContentByteArray.Length / 4194304  ; i++)
                var blockId = Convert.ToBase64String(Encoding.UTF8.GetBytes(Guid.NewGuid().ToString()));
                var uploadBlockRequest = new UploadBlockRequest()
                    BlockId = blockId,
                    BlockData = fileContentByteArray.Skip(i * 4194304).Take(4194304).ToArray(),
                    FileContinuationToken = initializeFileBlocksUploadResponse.FileContinuationToken

                var uploadBlockResponse = (UploadBlockResponse)svc.Execute(uploadBlockRequest);

            var commitFileBlocksUploadRequest = new CommitFileBlocksUploadRequest
                FileContinuationToken = initializeFileBlocksUploadResponse.FileContinuationToken,
                FileName = fileName,
                MimeType = System.Web.MimeMapping.GetMimeMapping(fileName),
                BlockList = lstBlock.ToArray()


            var commitFileBlocksUploadResponse = (CommitFileBlocksUploadResponse)svc.Execute(commitFileBlocksUploadRequest);

Author: Nishant Rana

I love working in and sharing everything about Microsoft.NET technology !

10 thoughts on “How to – Upload File to File Column using InitializeFileBlocksUpload and UploadBlock Request (Dynamics 365/ CRM)”

  1. Hi Nishant – I’m not sure if this was you intention but the code sample will never upload the contents of a file smaller than 4mb as the loop to generate upload block request will never be entered. Just an FYI for other readers.


      1. That is correct actually,
        If your fileContentByteArray.Length is less then 4194304 (4 MB), the result of that would be o.012345 something. Given the for-loop condition (for (int i = 0; i < fileContentByteArray.Length / 4194304 ; i++)), for-loop would not enter because result is 0 (zero) since devided result is an integer (I is an integer and result of fileContentByteArray.Length is integer as well).. unless you convert it to double:
        – for (int i = 0; i < (double)fileContentByteArray.Length / 4194304 ; i++)
        This way code will enter the for-loop and everything works fine after that.


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