Error Linq to Entities Datetime

Question

I have the following code

var dates = query.Select(
                 x => DateTime.ParseExact(x.Date, "yyyy-MM", CultureInfo.InvariantCulture));

var minDate = dates.Min(x => x);

But When I execute that, I get the exception

System.Data.Entity.dll but was not handled in user code

Additional information: LINQ to Entities does not recognize the method 'System.DateTime ParseExact(System.String, System.String, System.IFormatProvider)' method, and this method cannot be translated into a store expression.

What am I doing wrong? And how I can fix that?

Answer 1

Well, the error is actually quite clear. There is no translation in Linq to Entities of ParseExact to SQL.

Remember, Entity Framework, under the covers, converts the query to a SQL command or set of commands. If EF doesn't know how to translate something, it throws this error.

One possible solution, while not terribly efficient, is to convert the IQueryable to IEnumerable, which will allow you to execute the statement.

var dates = query.ToList().Select(
             x => DateTime.ParseExact(x.Date, "yyyy-MM", CultureInfo.InvariantCulture));