How to convert a type specified to a object type in IL.

 

There are two kinds of type in the IL: value type and non-value type. It can be judged from the IsValueType property of a object type.  e.g.  typeof(String).IsValueType.

ValueType includes Int(16, 32, 63), float(Single), Double, and so on.

No-ValueType includes String, Custom-Class and so on.

 

When you convert a type specified to a object type, if the type specified is a valuetype, the unbox.any instruction is used, else the castclass instruction be used. Please look the sample as follow:

 

Valuetype

 

.method private hidebysig instance float32

        TTT(object s) cil managed

{

  // Code size       12 (0xc)

  .maxstack  1

  .locals init ([0] float32 CS$1$0000)

  IL_0000:  nop

  IL_0001:  ldarg.1

  IL_0002:  unbox.any  [mscorlib]System.Single

  IL_0007:  stloc.0

  IL_0008:  br.s       IL_000a

  IL_000a:  ldloc.0

  IL_000b:  ret

} // end of method Form1::TTT

 

Non ValueType

 

.method private hidebysig instance string

        PPP(object s) cil managed

{

  // Code size       12 (0xc)

  .maxstack  1

  .locals init ([0] string CS$1$0000)

  IL_0000:  nop

  IL_0001:  ldarg.1

  IL_0002:  castclass  [mscorlib]System.String

  IL_0007:  stloc.0

  IL_0008:  br.s       IL_000a

  IL_000a:  ldloc.0

  IL_000b:  ret

} // end of method Form1::PPP