Convert Expression>> to Expression>

Question

I have some method:

public void Foo(Expression<Func<TModel, IEnumerable>> expression) {
  // foo
}

and I have variable:

Expression<Func<TModel, IList<TItem>>> expression;

How I can pass my variable to Foo?

With **much** effort. See my own question [here](http://stackoverflow.com/q/2797261/50079); read at the very least [my answer](http://stackoverflow.com/a/10467736/50079) (as the accepted one does not answer the most important part of your question) *and* the comments. I 'm not marking it as a dupe, leaving that for you to decide. — Jon, May 25 '12 at 10:25

score 4 · Accepted Answer · answered May 25 '12 at 10:30

4

You have to convert your expression variable:

var exp = Expression.Lambda<Func<TModel, IEnumerable>>(expression.Body, expression.Parameters);
Foo(exp);

answered May 25 '12 at 10:30

Balazs Tihanyi

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There will be InvalidCastException on casting to Expression>. Without casting pass a LambdaExpression to Foo will cause compiler error. – Dennis May 25 '12 at 10:47
@Dennis My solution doesn't use casting so it works without error. – Balazs Tihanyi May 25 '12 at 11:09
My bad. I've missed using of generic overload `Expression.Lambda`. – Dennis May 25 '12 at 11:15

score 2 · Answer 2 · answered May 25 '12 at 10:45

Use this:

    public Expression<Func<TModel, IEnumerable>> ConvertExpression<TModel, TItem>(Expression<Func<TModel, IList<TItem>>> expression)
    {
        return (Expression<Func<TModel, IEnumerable>>)Expression
            .Lambda(Expression.Convert(expression.Body, typeof(IEnumerable)), expression.Parameters);
    }

Convert Expression>> to Expression>

2 Answers2