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

Answer 1

In my case it was because of the length of the database field is less than the length of the input field.

database table

create table user(
  Username nvarchar(5) not  null
);

My input

User newUser = new User()
{
   Username = "123456"
};

the value for Username length is 5 which is lessthan 6

...this may help someone