How to convert an Expression<Func<T, bool>> to a Predicate<T>
I have a method that accepts an Expression<Func<T, bool>>
as a parameter. I would like to use it as a predicate in the List.Find() method, but I can't seem to convert it to a Predicate which List takes. Do you know a simple way to do this?
public IList<T> Find<T>(Expression<Func<T, bool>> expression) where T : class, new()
{
var list = GetList<T>();
var predicate = [what goes here to convert expression?];
return list.Find(predicate);
}
Update
Combining answers from tvanfosson and 280Z28, I am now using this:
public IList<T> Find<T>(Expression<Func<T, bool>> expression) where T : class, new()
{
var list = GetList<T>();
return list.Where(expression.Compile()).ToList();
}
Func<T, bool> func = expression.Compile();
Predicate<T> pred = t => func(t);
Edit: per the comments we have a better answer for the second line:
Predicate<T> pred = func.Invoke;
Another options which hasn't been mentioned:
Func<T, bool> func = expression.Compile();
Predicate<T> predicate = new Predicate<T>(func);
This generates the same IL as
Func<T, bool> func = expression.Compile();
Predicate<T> predicate = func.Invoke;
I'm not seeing the need for this method. Just use Where().
var sublist = list.Where( expression.Compile() ).ToList();
Or even better, define the expression as a lambda inline.
var sublist = list.Where( l => l.ID == id ).ToList();