CSDL File

What are CSDL files and how to open them

Are you having problems opening a CSDL file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CSDL files.

What is a CSDL file?

A .CSDL file is an ADO.NET Conceptual Schema Definition Language file.

ADO.NET Conceptual Schema Definition Language format stores a conceptual data model used by Microsoft's Entity Framework to represent the domain or business objects of an application. It defines entities, their properties, relationships and functions as an application's "conceptual schema," independent of how the data is actually stored. A developer designs this model using visual tools or code generation; at build time the metadata in this format helps map between the conceptual design and the actual database via separate mapping and storage schema formats. It enables querying and manipulation of data via the conceptual model rather than directly against database tables.

Files are produced by Microsoft tools (for example the Entity Framework Designer) when building an Entity Data Model (EDM). They are output as XML documents that conform to CSDL specifications during runtime; typically during build process, an integrated ".edmx" file is split into several artifacts including this format for the conceptual layer. The format is read by Entity Framework at runtime to load the conceptual schema into metadata objects, which then serve queries written against the conceptual model.

Internally the format is XML beginning with an XML declaration header (for example version 1.0 encoding UTF-8) followed by elements such as Schema, EntityType, Property, NavigationProperty, EntityContainer, EntitySet, and Association to declare types, relationships, and containers. Keywords like Namespace, Nullable, MaxLength, String, Int32 and Boolean appear; the XML namespace is typically one of Microsoft's "schemas.microsoft.com/ado/…/edm" URIs identifying CSDL version.

Byte‐level signatures include the UTF-8 XML declaration preceded by a possible BOM, and internal strings such as SCHEMAS.MICROSOFT.COM, ENTITYTYPE NAME, PROPERTY NAME, ENTITYSET, NAMESPACE, NULLABLE, and others consistent with CSDL syntax.

How to open CSDL files

Important: Different programs may use files with the CSDL file extension for different purposes, so unless you are sure which format your CSDL file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: September 19, 2026

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