Validation failed for one or more entities. See 'EntityValidationErrors' property for more details [duplicate]

Answer 1

I faced this error before

when I tried to update specific field in my model in entity framwork

Letter letter = new Letter {ID = letterId, ExportNumber = letterExportNumber,EntityState = EntityState.Modified};
LetterService.ChangeExportNumberfor(letter);
//----------


public int ChangeExportNumber(Letter letter)
    {
        int result = 0;
        using (var db = ((LettersGeneratorEntities) GetContext()))
        {
            db.Letters.Attach(letter);
            db.Entry(letter).Property(x => x.ExportNumber).IsModified = true;
            result += db.SaveChanges();
        }
        return result;
    }

and according the above answers

I found the Validation message The SignerName field is required.

which pointing to field in my model

and when I checked my database schema I found

so off coure ValidationException has its right to raise

and according to this field I want it to be nullable, (I dont know how I messed it)

so I changed that field to allow Null, and by this my code will not give me this error again

so This error maybe will happened if you invalidate Your Data integrity of your database