Gets or sets the DbExpression that defines the argument.
Assembly: System.Data.Entity (in System.Data.Entity.dll)
Derived expression types might perform stricter type checks when the property is set. For example, DbDistinctExpression requires that its argument expression has a collection result type. Typically, derived expression types will not allow to be set to an expression with a result type that is not equal or promotable to the result type of the current value.