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Business Central API Integration with Third-Party Software Using POST for BLOB Field

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Posted on by Suketu Piprotar

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Hi Everyone,

I am currently working on integrating Microsoft Dynamics 365 Business Central with a third-party application. As part of this integration, the third-party software needs to send a file to Business Central via an API (Page, Codeunit, or Query). This file will be stored in a field of type BLOB.

At present, I have exposed a Page API, and they are able to send the file using a PATCH request. However, the third-party system requires a POST request instead of PATCH.

Could anyone advise on the recommended approach to support POST requests for uploading BLOBs to Business Central? Would it be more appropriate to implement this through a custom API Page or a Codeunit, and how should the BLOB handling be structured?

Thank you in advance for your support!

Best Regards,

Suketu Piprotar

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Dynamics 365 Business Central

Microsoft Dynamics NAV

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Kamal Khakhkhar 3,428 on at

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Hii there ,

If the third-party can't support base64, create a proxy in Azure to transform binary to base64 before sending to BC.

also you can create a API Pages , Codeunit , table as per requirement .

If you found your reference/Answer . please mark it answered.

Thank You.

Kamal Khakhkhar

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Jainam M. Kothari 17,024 Super User 2026 Season 1 on at

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May this can help : https://learn.microsoft.com/en-us/dynamics365/business-central/dev-itpro/developer/methods-auto/httpclient/httpclient-post-method

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Jeffrey Bulanadi 9,128 Super User 2026 Season 1 on at

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Hi Suketu,

You're absolutely right to explore alternatives to PATCH, especially when the third-party system mandates a POST request for file uploads. BC’s standard API pages typically support PATCH for updating BLOBs, but you can absolutely support POST by designing a custom API Page or Codeunit.

Let’s break it down:

1. Why PATCH works by default and POST doesn’t
Standard API Pages in BC are designed for entity updates, which is why PATCH is the default method for modifying BLOB fields. POST is reserved for creating new records, and doesn’t natively support BLOB streaming unless explicitly handled.

2. Recommended approach: Custom API Page + Codeunit
To support POST for BLOB uploads:

Create a custom API Page that exposes the record with the BLOB field

Add a Codeunit with a procedure that accepts a Text or InStream parameter

Use CreateInStream and CreateOutStream to handle the BLOB field

Trigger the Codeunit via an action on the API Page, or expose it as a separate endpoint

Example structure:

al

procedure UploadFileViaPost(var Rec: Record "YourTable"; FileContent: Text) var OutStream: OutStream; begin Clear(Rec.YourBlobField); Rec.Modify(true); Rec.YourBlobField.CreateOutStream(OutStream); OutStream.WriteText(FileContent); Rec.Modify(true); end;

You can also use HttpContent and HttpRequestMessage if you're building the integration from BC outward.

3. Alternative: Use Media or MediaSet fields
If the file is an image or document, consider using Media or MediaSet fields instead of BLOB. These are optimized for file handling and support POST natively via the standard API.

4. Key considerations

Ensure the BLOB field is marked with DataClassification = ToBeClassified

Use DelayedInsert = true on the API Page to allow POST before record creation

Validate stream closure to avoid errors like “Read called with an open stream”

Helpful references:

Handling BLOB fields on APIs – Stefano Demiliani
Posting JSON Data in BLOB via POST – Stack Overflow
BC API Overview – Microsoft Learn

If you find this helpful, feel free to mark this as the suggested or verified answer.

Cheers
Jeffrey

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YUN ZHU 101,995 Super User 2026 Season 1 on at

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Hi, a simple example, hopefully it will give you some hints.

Dynamics 365 Business Central: Using OData V4 unbound action (Codeunit API?) to communicate and exchange data seamlessly

https://yzhums.com/60916/

Thanks.

ZHU

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Sohail Ahmed 11,177 Super User 2026 Season 1 on at

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You can support POST for BLOB upload using a custom API Codeunit with InStream/OutStream. Here's a short AL example:

codeunit 50100 BlobUpload

{

[ServiceEnabled]

procedure UploadFile(FileName: Text; Base64Content: Text)

var

RecRef: RecordRef;

InStr: InStream;

OutStr: OutStream;

TempBlob: Codeunit "Temp Blob";

begin

TempBlob.CreateOutStream(OutStr);

OutStr.WriteText(Base64Content);

TempBlob.CreateInStream(InStr);

TempBlob.ToRecord(SomeTargetRecord); // Your table with BLOB field

SomeTargetRecord.CalcFields("Your BLOB Field");

SomeTargetRecord."Your BLOB Field".CreateInStream(InStr);

// Save the BLOB content as needed

SomeTargetRecord.Modify();

end;

}

This allows third-party apps to POST base64 files into BC via a Codeunit.

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Gerardo Rentería Ga... 27,280 Most Valuable Professional on at

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Hi, good day
I hope this can help you, and give you some hints.

Dynamics 365 Business Central: handling BLOB fields on APIs – Stefano Demiliani

Best Regards
Gerardo

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CU16060844-1 2 on at

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If a third-party system specifically requires a POST, a custom Codeunit exposed as a web service is often a cleaner approach, especially when handling file uploads and BLOB streams. I myself was recently looking for alternatives to photo editing software on Mac and came across https://setapp.com/app-reviews/snapseed-alternative-for-mac which is a good example of how specialized comparison guides can help you evaluate your tool choices when building integrations around external platforms. They are very helpful and may be able to get your request to work. I would add that for Business Central, the Codeunit also gives you more control over validation, error handling, and future extensibility than the standard API page.

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Grigorios Mavrogeorgis 2,554 Super User 2026 Season 1 on at

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Hi Suketu,

the PATCH thing isn't really a limitation, it's just OData semantics — you PATCH the media or $value endpoint because the record already exists, POST is for creating. So if their system only does POST, don't fight that endpoint.
Better to expose the BLOB on your API page as a base64 text field, and let them POST the whole record as JSON with the file content sitting in that field. On insert you decode the base64 back into the BLOB. POST works naturally then, because it's an insert not an update.

Other way is a bound action — those get called with POST anyway — and you read the content from the request body in a codeunit. I'd go the API page plus base64 field route myself, easier for them to consume.
One thing that bites — base64 grows the payload about a third, and there's request size limits, so for big files it gets messy.

Glad to help - follow up if anything is unclear.
► If this solved it, marking it verified helps others too.
Regards,
Grigorios Mavrogeorgis
Business Central Consultant & AL Developer
Work: Gmsoft Limited
Blog: insidebusinesscentral
LinkedIn: linkedin.com/in/gregorymavrogeorgis

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