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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(); } 
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Lance Fisher Avatar asked Aug 01 '09 23:08

Lance Fisher


2 Answers

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; 
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Sam Harwell Avatar answered Sep 25 '22 12:09

Sam Harwell


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; 
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Jon Skeet Avatar answered Sep 24 '22 12:09

Jon Skeet