Why Am I Getting a 'Validation Failed' Exception When Saving Data to SQL Server Using Entity Framework?

Validation Failed Exception when Saving to SQL Server Using Entity Framework

Entity Framework is a powerful ORM (Object-Relational Mapping) framework that enables developers to work with relational databases using object-oriented programming languages like C#. However, one common issue that can arise while working with Entity Framework is the "Validation failed for one or more entities" exception when saving changes to the database.

Reason for the Exception

The error message typically indicates that the data being saved to the database violates database constraints. In this specific case, the issue may stem from the different data types being used for date and time values in the database and in the Entity class.

Solution: Casting to the Appropriate Data Types

To resolve this issue, the data types in the Entity class need to be cast to match the database data types before saving changes. In this case, the DateTime and TimeSpan data types in the Event class should be cast to Date and Time data types before being saved to the database.

Here's how to do it in the code:

// Convert EventDate to Date datatype
Event event = this.storeDB.Events.Find(id);
event.EventDate = event.EventDate.Date;

// Convert StartTime and EndTime to Time datatype
event.StartTime = new TimeSpan(event.StartTime.Hours, event.StartTime.Minutes, 0);
event.EndTime = new TimeSpan(event.EndTime.Hours, event.EndTime.Minutes, 0);

// Save changes to the database
this.storeDB.SaveChanges();
RedirectToAction("Index");

By casting the data types to the correct formats, the data being saved to the database will now comply with the database constraints, resolving the "Validation failed" exception.

Additional Note:

If you continue to encounter data saving issues, you can extract more information about the validation errors by using the DbEntityValidationException's EntityValidationErrors property, as shown in the provided answer.

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