protected virtual LambdaExpression CreateLambaExpression(Type tSource)
{
Debug.Assert(tSource != null);
Debug.Assert(!string.IsNullOrEmpty(Id.LookupId));
return(ExpressionFactory.CreateFieldSelectorLambda(tSource, Id.LookupId));
}
protected virtual MethodCallExpression GetPropertyOrFieldAggregateExpression(Type tSource, Expression param)
{
// otherwise the target of the aggregate is a property on the source type such as Avg(Age)
Expression lambda = ExpressionFactory.CreateFieldSelectorLambda(tSource, SourceFieldName);
return(Expression.Call(EvaluatatorType, Name, new Type[] { tSource }, param, lambda));
}
private static Expression CreateKeySelector <T>(string name, Type keyType, ParameterExpression param)
{
// special case for when the key is the data item, not a field of the data item
if (name.Equals("this", StringComparison.OrdinalIgnoreCase) || name.Equals("that", StringComparison.OrdinalIgnoreCase))
{
return(ExpressionFactory.CreateIdentitySelector <T, T>());
}
return(ExpressionFactory.CreateFieldSelectorLambda(param, name, keyType));
}
protected override MethodCallExpression GetPropertyOrFieldAggregateExpression(Type tSource, Expression param)
{
LambdaExpression lambda = ExpressionFactory.CreateFieldSelectorLambda(tSource, SourceFieldName);
return(Expression.Call(EvaluatatorType, Name, new Type[] { tSource, tSource.GetFieldType(SourceFieldName) }, param, lambda));
}