private static Expression <T> Compose <T>(this Expression <T> first, Expression <T> second, Func <Expression, Expression, Expression> merge) { // build parameter map (from parameters of second to parameters of first) var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f); // replace parameters in the second lambda expression with parameters from the first var secondBody = RebindParameterVisitor.ReplaceParameters(map, second.Body); // apply composition of lambda expression bodies to parameters from the first expression return(Expression.Lambda <T>(merge(first.Body, secondBody), first.Parameters)); }
public static Expression <T> Compose <T>( this Expression <T> first, Expression <T> second, Func <Expression, Expression, Expression> merge) { var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }) .ToDictionary(p => p.s, p => p.f); var secondBody = RebindParameterVisitor.ReplaceParameters(map, second.Body); return(Expression.Lambda <T>(merge(first.Body, secondBody), first.Parameters)); }