Confused about auto property IL accessing two arguments rather than one

Question

Given the following auto property:

public string Name { get; set; }

I analysed it's IL using ILDASM and was curious about the result:

.method public hidebysig specialname instance void 
        set_Name(string 'value') cil managed
{
  .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 ) 
  // Code size       8 (0x8)
  .maxstack  8
  IL_0000:  ldarg.0
  IL_0001:  ldarg.1
  IL_0002:  stfld      string Strings.Person::'<Name>k__BackingField'
  IL_0007:  ret
} // end of method Person::set_Name

I can see that the method takes in a parameter named value, which corresponds to the call ldarg.0. However, the call to ldarg.1 caught me out as I cannot see a second parameter in the method signature.

Was hoping that someone could explain what's going on here please?

Answer 1

• ldarg.0 loads the hidden this parameter.
• ldarg.1 loads value
• stfld assigns the value on top of the stack to a field in the object below it on the stack.