Entity Framework Pitfalls: String Length Validation

If you want to validate the maximum number of characters that a string property can take, you might be lured into using MaxLengthAttribute. However, this won’t give you what you want: what this attribute does is, when a model is being generated, it provides the maximum length of the string field in the database, but does not perform any kind of pre-insert or pre-update validation. For that, you need to use StringLengthAttribute. This one is indeed a validation attribute, inheriting from ValidationAttribute, and will be called when EF is about to persist your entity, or when ASP.NET MVC validates a model as a consequence of a post. You can specify both the minimum (MinimumLength) as well as the maximum length (MaximumLength).


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