Dynamic Linq Property Converting to Sql

Posted by Matthew Hood on Stack Overflow See other posts from Stack Overflow or by Matthew Hood
Published on 2010-04-13T11:50:15Z Indexed on 2010/04/13 11:52 UTC
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I am trying to understand dynamic linq and expression trees. Very basically trying to do an equals supplying the column and value as strings. Here is what I have so far

 private IQueryable<tblTest> filterTest(string column, string value)
    {
        TestDataContext db = new TestDataContext();

        // The IQueryable data to query.
        IQueryable<tblTest> queryableData = db.tblTests.AsQueryable();

        // Compose the expression tree that represents the parameter to the predicate.
        ParameterExpression pe = Expression.Parameter(typeof(tblTest), "item");


        Expression left = Expression.Property(pe, column);
        Expression right = Expression.Constant(value);
        Expression e1 = Expression.Equal(left, right);

        MethodCallExpression whereCallExpression = Expression.Call(
            typeof(Queryable),
            "Where",
            new Type[] { queryableData.ElementType },
            queryableData.Expression,
            Expression.Lambda<Func<tblTest, bool>>(e1, new ParameterExpression[] { pe }));

        // Create an executable query from the expression tree.
        IQueryable<tblTest> results = queryableData.Provider.CreateQuery<tblTest>(whereCallExpression);

        return results;
    }

That works fine for columns in the DB. But fails for properties in my code eg

public partial class tblTest
{
    public string name_test
    {  get { return name; }  }
}

Giving an error cannot be that it cannot be converted into SQL. I have tried rewriting the property as a Expression<Func but with no luck, how can I convert simple properties so they can be used with linq in this dynamic way?

Many Thanks

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