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Text output of Blob field in API pages

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Hello, I have extended a base table to create a custom field of type blob and can input text in that , I created API page for the same table, I am getting proper output of other fields but not getting text output of that particular blob datatype field, Plz suggest me code for this one

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Dynamics 365 Business Central

Dynamics 365 Business Central migration

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Dr Gomathi MVP, MCT... 395 Super User 2025 Season 2 on at

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I'll help you handle the Blob field data in your Business Central API page. Here's how to properly expose and get text output from a Blob field:

First, define the Blob field in your table extension

tableextension 50100 "YourTableExt" extends "Your Base Table" { fields { field(50100; "Your Blob Field"; Blob) { Caption = 'Your Blob Field'; } } }

Create helper methods to read/write Blob data

codeunit 50100 "Blob Handler" { procedure BlobToText(BlobField: Blob) ReturnValue: Text var InStream: InStream; Line: Text; begin if BlobField.HasValue() then begin BlobField.CreateInStream(InStream, TEXTENCODING::UTF8); InStream.ReadText(ReturnValue); end; end; procedure TextToBlob(var BlobField: Blob; TextValue: Text) var OutStream: OutStream; begin Clear(BlobField); BlobField.CreateOutStream(OutStream, TEXTENCODING::UTF8); OutStream.WriteText(TextValue); end; }

In your API page, add a text field that represents the Blob data

page 50100 "Your API Page" { APIVersion = 'v2.0'; APIPublisher = 'yourPublisher'; APIGroup = 'yourGroup'; EntityName = 'yourEntity'; EntitySetName = 'yourEntities'; PageType = API; SourceTable = "Your Base Table"; layout { area(Content) { field(blobContent; GetBlobContent()) { Caption = 'Blob Content'; ApplicationArea = All; } // ... other fields } } var BlobHandler: Codeunit "Blob Handler"; local procedure GetBlobContent(): Text begin exit(BlobHandler.BlobToText(Rec."Your Blob Field")); end; // If you need to handle incoming data trigger OnInsertRecord(BelowxRec: Boolean): Boolean begin BlobHandler.TextToBlob(Rec."Your Blob Field", blobContent); end; }

Key Points to Remember:

Always use proper encoding (UTF8 recommended)

Handle cases where the Blob might be empty

Consider adding error handling for large text content

Test both reading and writing scenarios thoroughly

Hope this will work.

Please comment if you have any queries.

If this helps, kindly mark this as a answer

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Gerardo Rentería Ga... 25,213 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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Teddy Herryanto (Th... 14,284 Super User 2025 Season 2 on at

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BLOB fields are not exposed via APIs. This is because you can have a huge amount of data inside the BLOB.

You can use Stefano blog post to get the BLOB value.

https://demiliani.com/2020/01/24/dynamics-365-business-central-handling-blob-fields-on-apis/

Or you can create a function to convert that blob to text. You can check the GetWorkDescription procedure on Sales Header for example on how to convert.

procedure GetWorkDescription() WorkDescription: Text

var

TypeHelper: Codeunit "Type Helper";

InStream: InStream;

begin

CalcFields("Work Description");

"Work Description".CreateInStream(InStream, TEXTENCODING::UTF8);

exit(TypeHelper.TryReadAsTextWithSepAndFieldErrMsg(InStream, TypeHelper.LFSeparator(), FieldName("Work Description")));

end;

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YUN ZHU 95,331 Super User 2025 Season 2 on at

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Hi, hope the following can give you some hints as well.

https://yzhums.com/27951/

Thanks.

ZHU

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Khushbu Rajvi. 20,347 Super User 2025 Season 2 on at

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Hope this helps as well: https://community.dynamics.com/blogs/post/?postid=2bf9715c-7fcb-46af-aabe-c9f032eb053a

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Rudylar 114 on at

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Hi, I tried all different suggested solutions. When I export the Blob multiline content, I almost always get ASCII char such as \u0003 or \u0016 or \n or \u001e.

I tried using encode UTF8, UTF16, WindowsText, MSDOS. Same result.
Any idea ? Thanks

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OussamaSabbouh 5,659 on at

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Hello,

API pages can’t return BLOB fields directly.
To expose your BLOB as text, add a text variable field on the API page and use Get/Set procedures with InStream / OutStream inside the table extension.

Pattern:

On API page OnAfterGetRecord → BlobText := Rec.GetMyBlobText();

On Validate → Rec.SetMyBlobText(BlobText);

In the table extension, implement:

procedure GetMyBlobText(): Text
procedure SetMyBlobText(NewText: Text)

Only this wrapper approach works — exposing the BLOB itself will always return empty.

Regards,
Oussama Sabbouh

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