How to build generic type parameter

Question

I have a question. How can I build a generic type parameter? I am trying to build an expression tree and I have the following line to build:

var expression = Expression
                .Lambda<Func<T, bool>>(
                    operation,
                    new ParameterExpression[] {parameter});

So it is expected that I specify type parameter for T in .Lambda> but the type parameter T in not known until runtime.

Please help. Thanks

Answer 1

Well, you could write it in a generic method:

public Expression<Func<T,bool>> BuildExpression<T>(...)
{
    // Whatever you need to do
    var expression = Expression
            .Lambda<Func<T, bool>>(
                operation,
                new ParameterExpression[] {parameter});
}

... and then call that method via reflection. Alternatively:

• You could call the generic Expression.Lambda method via reflection
• You could call the non-generic overload of Expression.Lambda

Without knowing anything more about your requirements, it's very hard to give any advice about which of these would be the most suitable approach. Please edit your question to give more details.