Automatic Properties Backing Field Naming Conventions?

  • Thread starter Thread starter Joerg Battermann
  • Start date Start date
J

Joerg Battermann

Hello there,

does anyone know the precise naming conventions used for internal
backing fields for automatic properties? Something official besides
looking at the compiled assemblies that might let you 'assume' a
certain schema...

Cheers and thanks,
-jB
 
Joerg Battermann said:
does anyone know the precise naming conventions used for internal
backing fields for automatic properties? Something official besides
looking at the compiled assemblies that might let you 'assume' a
certain schema...
Click to expand...

I wouldn't make any assumptions. If you need direct access to the
fields, don't use automatic properties. The naming scheme is compiler-
dependent and unspecified; it could change between compiler versions.
 
Argh - ok that's bad (for me). Basically I have an oodbms attached to
some of my classes.. and adding indexes relies in knowing the field
names. Bad... but oh well.

Thanks Jon & Peter!
 
Joerg said:
Argh - ok that's bad (for me). Basically I have an oodbms attached to
some of my classes.. and adding indexes relies in knowing the field
names. Bad... but oh well.
Click to expand...

Hmm... well... the following code will give you the field for
automatically generated properties on all but the most crazy compilers,
where it could potentially do odd things (for example, if the automatic
property's getter strangly called a method before accessing the field
and that method happened to contain 0x7B in its token).

Cecil would be useful here and could parse the IL instead of guessing
that the first instance of 0x7B is the ldfld instruction so the token
will come next.

Having said that, it does work for any reasonable compiler and I wanted
to keep the code simple:

private static FieldInfo GetBackingField(PropertyInfo property)
{
if (!(property.CanRead && property.CanWrite))
{
throw new NotSupportedException("Not an automatic property");
}

byte[] getter =
property.GetGetMethod().GetMethodBody().GetILAsByteArray();
byte ldfld = (byte)(property.GetGetMethod().IsStatic ?
OpCodes.Ldsfld : OpCodes.Ldfld).Value;
byte[] fieldToken = getter.SkipWhile(b => b !=
ldfld).Skip(1).Take(4).ToArray();
if (fieldToken.Length != 4)
{
throw new NotSupportedException("Not an automatic property");
}
FieldInfo field =
property.DeclaringType.Module.ResolveField(BitConverter.ToInt32(fieldToken,
0));
if (field == null)
{
throw new NotSupportedException("Not an automatic property");
}

//Not sure about this: compilers don't strictly have to add this
attribute.
if (!field.IsDefined(typeof(CompilerGeneratedAttribute), false))
{
throw new NotSupportedException("Not an automatic property");
}
return field;
}

Alun Harford
 
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