NJection.LambdaConverter is an open-source .NET assembly for converting delegates resolved from methods/constructors to expression trees.

github repository:
https://github.com/sagifogel/NJection.LambdaConverter

Converting a static delegate


public class Program
{
      private static void Main(string[] args) {
           var lambda = Lambda.TransformMethodTo<Func<string, int>>()
                              .From(() => Parse)
                              .ToLambda();            
      }

      private static int Parse(string value) {
           return int.Parse(value);
      }
}

Converting an instance delegate


public class Sample
{
      public int Parse(string value) {
          return int.Parse(value);
      }
}

public class Program
{
      private static void Main(string[] args) {
           var sample = new Sample();
           var lambda = Lambda.TransformMethodTo<Func<string, int>>()
                              .From(() => sample.Parse)
                              .WithContextOf<Sample>(sample)
                              .ToLambda();              
      }
}

Converting a constructor


public class Sample
{
     public int Value { get; set; }

     public Sample(int i) {
          Value = i;
     }
}

public class Program
{
      private static void Main(string[] args) {
           var ctor = typeof(Sample).GetConstructor(new Type[] { typeof(int) });
           var resolver = new ConstructorResolver(ctor);
           var lambda = Lambda.ResolveConstructorTo<Func<int, Sample>>(resolver)
                              .ToLambda();            
      }
}

Converting a generic delegate


public class Program
{
      private static void Main(string[] args) {
          var lambda = Lambda.TransformMethodTo<Func<string, DateTime>>()
                             .From(() => Parse<DateTime>)
                             .ToLambda();           
      }

      private static T Parse<T>(string value) where T : struct {
           return (T)Enum.Parse(typeof(T), value);
      }
}

Converting a custom delegate

public class Program
{	
      private delegate int CustomDelegate(string value);

      private static void Main(string[] args) {
          var lambda = Lambda.TransformMethodTo<CustomDelegate>()
                             .From(() => Parse)
                             .ToLambda();           
      }

      private static int Parse(string value) {
          return int.Parse(value);
      }
}