Converting Lambda expression to sql query

Question

I started a project that will allow me to create sql queries using lambda expressions.

for some reason when I'm trying the following code, the lambda injected with "Convert" method please help me understand the reason and how I can avoid it.

GroupBy function:

public QueryBuilder<T> GroupBy(params Expression<Func<T, object>>[] expression)
{
    _groupBy.AddRange(expression);
    return this;
}

Usage example:

query.GroupBy(x=>x.IntExample,x=>x.StringExample)

from the immediate:

 expression
 {System.Linq.Expressions.Expression<System.Func<Tests.Example,object>>[2]}
 [0]: {x => Convert(x.IntExample)}
 [1]: {x => x.StringExample}

Fill free to fork the project: https://github.com/matanshidlov/Lambda-To-Sql/tree/master/Lambda-To-Sql

try this query.GroupBy(x=> x.IntExample, x.StringExample)

Feras Salim
– Feras Salim

2015-06-27 16:39:21 +00:00
Commented Jun 27, 2015 at 16:39 — Feras Salim
– Feras Salim, Commented Jun 27, 2015 at 16:39
I cant do this, that code doesn't pass compilation

Matan Shidlov
– Matan Shidlov

2015-06-27 16:42:58 +00:00
Commented Jun 27, 2015 at 16:42 — Matan Shidlov
– Matan Shidlov, Commented Jun 27, 2015 at 16:42

Olivier Jacot-Descombes · Accepted Answer · 2015-06-27 17:05:04Z

1

object is a reference type. int is a value type. In order to convert an int into an object, and thus into a reference type, the int has to be boxed. Boxing involves creating a reference type object as a wrapper around the int. This is what Convert does.

See: Boxing and Unboxing (C# Programming Guide)
and also: Expression.Convert Method

edited Jun 27, 2015 at 17:05

answered Jun 27, 2015 at 16:40

Olivier Jacot-Descombes

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