To work around this restriction, you can manually construct an expression (Source)
C#
static Expression<Func<TElement, bool>> BuildContainsExpression<TElement, TValue>(
Expression<Func<TElement, TValue>> valueSelector, IEnumerable<TValue> values)
{
if (null == valueSelector) { throw new ArgumentNullException("valueSelector"); }
if (null == values) { throw new ArgumentNullException("values"); }
ParameterExpression p = valueSelector.Parameters.Single();
// p => valueSelector(p) == values[0] || valueSelector(p) == ...
if (!values.Any())
{
return e => false;
}
var equals = values.Select(value => (Expression)Expression.Equal(valueSelector.Body, Expression.Constant(value, typeof(TValue))));
var body = equals.Aggregate<Expression>((accumulate, equal) => Expression.Or(accumulate, equal));
return Expression.Lambda<Func<TElement, bool>>(body, p);
}
Using this utility method,
var query2 = context.Entities.Where(BuildContainsExpression<Entity, int>(e => e.ID, ids));
VB.Net
Public Shared Function BuildContainsExpression(Of TElement, TValue)( _
ByVal valueSelector As Expression(Of Func(Of TElement, TValue)), _
ByVal values As IEnumerable(Of TValue) _
) As Expression(Of Func(Of TElement, Boolean))
' validate arguments
If IsNothing(valueSelector) Then Throw New ArgumentNullException("valueSelector")
If IsNothing(values) Then Throw New ArgumentNullException("values")
Dim p As ParameterExpression = valueSelector.Parameters.Single()
If Not values.Any Then
Return _
Function(e) False
End If
Dim equals = values.Select( _
Function(v) _
Expression.Equal(valueSelector.Body, Expression.Constant(v, GetType(TValue))) _
)
Dim body = equals.Aggregate( _
Function(accumulate, equal) _
Expression.Or(accumulate, equal) _
)
Return Expression.Lambda(Of Func(Of TElement, Boolean))(body, p)
End Function
Using this utility method
Dim query = m_data. Offer
If (selectedSectors.Count > 0) Then
query = query.Where(BuildContainsExpression(Function(o As Offer) o.Value, selectedSectors))
End If
