Generate EF orderby expression by string

Question

I want to generate expression by string parameter,some code like:

private Expression> Generate(string orderby)
{
    switch (orderb         


        

Answer 1

Use a generic method. Since lambda expressions can only be assigned to strongly typed delegates or expressions, we must use an according temp. Then we can assign this temp to a variable typed as object. Finally we can return the result by casting to the result type.

public Expression> Generate(string orderby)
{
    object result;
    switch (orderby) {
        case "Time":
            Expression> temp1 = t => t.Time;
            result = temp1;
            break;
        case "Money":
            Expression> temp2 = t => t.RewardMoney;
            result = temp2;
            break;
        default:
            Expression> temp3 = t => t.Id;
            result = temp3;
            break;
    }
    return (Expression>)result;
}