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Why is my Entity Framework application throwing a MetadataException despite a correct connection string?

Patricia Arquette

Jan 22, 2025 pm 02:37 PM

Why is my Entity Framework application throwing a MetadataException despite a correct connection string?

Entity Framework MetadataException: Troubleshooting Guide

Symptom:

A MetadataException is thrown when creating an ObjectContext instance, even with a valid connection string in App.config and no recent EDMX or database modifications. The error indicates a failure to load metadata resources.

Causes and Solutions:

This exception typically stems from problems loading the EDMX file. Here are some common culprits:

Incorrect MetadataArtifactProcessing Setting: Verify that the MetadataArtifactProcessing property of your EDMX model is not set to "Copy to Output Directory." This setting can prevent the application from finding the necessary metadata.
Connection String Discrepancies: Double-check your connection string. Even seemingly minor changes, particularly those affecting assembly names, can invalidate it.
Embedded EDMX Problems: If you're embedding the EDMX into your assembly using a post-build event, carefully examine the configuration of this task for any errors or misconfigurations.

Further Diagnostics:

If the above steps don't resolve the issue, try these additional troubleshooting steps:

Connection String Verification: Thoroughly validate your connection string. Ensure the server name, database name, user credentials, and other details are accurate.
Post-Build Event Review: If using a post-build event, meticulously review its configuration and logs for any errors. Ensure it's successfully embedding the EDMX.
Reset MetadataArtifactProcessing: Explicitly reset the MetadataArtifactProcessing property to the correct value (likely "Content" or "Inherit").
EDMX Model Refresh: Try refreshing your EDMX model from the database. This can sometimes resolve inconsistencies.
Complete Rebuild: As a last resort, consider completely recreating the database, assemblies, and the EDMX model.

For comprehensive troubleshooting and advanced solutions, consult the relevant blog post (link not provided in original text).

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