C# Syntax – Is There a Reason to Prefer Lambda Syntax Even with One Parameter?

Looking at the compiled code through ILSpy, there actually is a difference in the two references. For a simplistic program like this:

namespace ScratchLambda
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;

    internal class Program
    {
        private static void Main(string[] args)
        {
            var list = Enumerable.Range(1, 10).ToList();
            ExplicitLambda(list);
            ImplicitLambda(list);
        }

        private static void ImplicitLambda(List<int> list)
        {
            list.ForEach(Console.WriteLine);
        }

        private static void ExplicitLambda(List<int> list)
        {
            list.ForEach(s => Console.WriteLine(s));
        }
    }
}

ILSpy decompiles it as:

using System;
using System.Collections.Generic;
using System.Linq;
namespace ScratchLambda
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            List<int> list = Enumerable.Range(1, 10).ToList<int>();
            Program.ExplicitLambda(list);
            Program.ImplicitLambda(list);
        }
        private static void ImplicitLambda(List<int> list)
        {
            list.ForEach(new Action<int>(Console.WriteLine));
        }
        private static void ExplicitLambda(List<int> list)
        {
            list.ForEach(delegate(int s)
            {
                Console.WriteLine(s);
            }
            );
        }
    }
}

If you look at the IL call stack for both, the Explicit implementation has a lot more calls (and creates a generated method):

.method private hidebysig static 
    void ExplicitLambda (
        class [mscorlib]System.Collections.Generic.List`1<int32> list
    ) cil managed 
{
    // Method begins at RVA 0x2093
    // Code size 36 (0x24)
    .maxstack 8

    IL_0000: ldarg.0
    IL_0001: ldsfld class [mscorlib]System.Action`1<int32> ScratchLambda.Program::'CS$<>9__CachedAnonymousMethodDelegate1'
    IL_0006: brtrue.s IL_0019

    IL_0008: ldnull
    IL_0009: ldftn void ScratchLambda.Program::'<ExplicitLambda>b__0'(int32)
    IL_000f: newobj instance void class [mscorlib]System.Action`1<int32>::.ctor(object, native int)
    IL_0014: stsfld class [mscorlib]System.Action`1<int32> ScratchLambda.Program::'CS$<>9__CachedAnonymousMethodDelegate1'

    IL_0019: ldsfld class [mscorlib]System.Action`1<int32> ScratchLambda.Program::'CS$<>9__CachedAnonymousMethodDelegate1'
    IL_001e: callvirt instance void class [mscorlib]System.Collections.Generic.List`1<int32>::ForEach(class [mscorlib]System.Action`1<!0>)
    IL_0023: ret
} // end of method Program::ExplicitLambda


.method private hidebysig static 
    void '<ExplicitLambda>b__0' (
        int32 s
    ) cil managed 
{
    .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = (
        01 00 00 00
    )
    // Method begins at RVA 0x208b
    // Code size 7 (0x7)
    .maxstack 8

    IL_0000: ldarg.0
    IL_0001: call void [mscorlib]System.Console::WriteLine(int32)
    IL_0006: ret
} // end of method Program::'<ExplicitLambda>b__0'

while the Implicit implementation is more concise:

.method private hidebysig static 
    void ImplicitLambda (
        class [mscorlib]System.Collections.Generic.List`1<int32> list
    ) cil managed 
{
    // Method begins at RVA 0x2077
    // Code size 19 (0x13)
    .maxstack 8

    IL_0000: ldarg.0
    IL_0001: ldnull
    IL_0002: ldftn void [mscorlib]System.Console::WriteLine(int32)
    IL_0008: newobj instance void class [mscorlib]System.Action`1<int32>::.ctor(object, native int)
    IL_000d: callvirt instance void class [mscorlib]System.Collections.Generic.List`1<int32>::ForEach(class [mscorlib]System.Action`1<!0>)
    IL_0012: ret
} // end of method Program::ImplicitLambda