Error: DbArithmeticExpression arguments must have a numeric common type.

From time to time you need to filter data by difference between two dates. For instance, you wanna take a difference between date from a record and Today.

Standard LINQ request will fail with the statement like the following:

var r = from e in Entity where e.Date.Subtract(DateTime.Today) <= 5;

1	var r = from e in Entity where e.Date.Subtract(DateTime.Today) <= 5;

In Entity Framework version 4 the new utility class has been introduced – EntityFunctions. With the method of this class you can rewrite the statement above like this:

var r = from e in Entity where EntityFunctions.DiffDays(DateTime.Today, e.Date) <= 5;

1	var r = from e in Entity where EntityFunctions.DiffDays(DateTime.Today, e.Date) <= 5;

For someone who cannot use EntityFunctions for any reason there is a workaround. Long story short, you should compare the dates. The following changes might be done:

var maxDate = DateTime.Today.AddDays(5);
var r = ... where e.Date <= maxDate;

1 2	var maxDate = DateTime.Today.AddDays(5); var r = ... where e.Date <= maxDate;

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