Entity Framework check for DbUpdateException before SaveChanges

Question

You will get a DbUpdateException if you try to save a string with length of 500 to a column in Sql Server which is a nvarchar(255).

Is there any way to check for this error before calling SaveChanges()? Maybe when adding the entity to context?

As the answer below states, yes you can do this. However, you really should be catching these errors before they become a problem. Validate the input before it gets anywhere near the context. — DavidG
– DavidG, Commented Jun 13, 2018 at 10:37
find the length of string and write comdition like if(len>255) throw err — Ratan Uday Kumar
– Ratan Uday Kumar, Commented Jun 13, 2018 at 10:38
@DavidG Yeah I've heard that you should validate before going to the context, but why is that? Because of performance? — skjold
– skjold, Commented Jun 14, 2018 at 11:16

CodeNotFound · Accepted Answer · 2018-06-13 10:40:37Z

2

Is there any way to check for this error before calling SaveChanges? Maybe when adding the entity to context?

Yes. It is possible by calling this method GetValidationErrors() on your DbContext like below but you will get the validation errors result only if you make use of data annoations attributes on your entity classes

var validationResults = dbContext.GetValidationErrors();

validationResults will contain a collection of DbEntityValidationResult so if empty then your tracked entities are valid. Then calling SaveChanges just after will not throw exception about data validation but you can still get some others exceptions which can be checked only on server side e.g. concurrency exception, unique or reference constraint exception, etc.

edited Jun 13, 2018 at 10:40

answered Jun 13, 2018 at 10:35

CodeNotFound

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4 Comments

skjold Over a year ago

Ok great! StringLength attribute works! Is there any way to use data annotations attributes to check decimal length aswell?

CodeNotFound Over a year ago

Yes it exists => RangeAttribute.

skjold Over a year ago

Alright, but how would you define a range of 0 to 16 digits?

CodeNotFound Over a year ago

@skjold this may help you.

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