Storing a Lambda Expression in a Variable

With C# 7.0 local functions

TResult matchDuplicates (T1 c) => _configuration = c;

A lambda expression is just a delegate that often maps to one of the Func<T1, T2, ..., TResult> variants.

Func<T1, TResult> myVar = c => _configuration = c;

Replacing TResult and T1 with the relevant types.

That might work for you.