Jason Bock
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More Attribute Description Information
OK, here’s the crux of the description problem. Here’s the CIL from the ServiceProcessDescriptionAttribute’s constructor:
.method public hidebysig specialname rtspecialname
instance void .ctor(string description) cil managed
{
// Code size 15 (0xf)
.maxstack 8
IL_0000: ldarg.0
IL_0001: ldc.i4.0
IL_0002: stfld bool System.ServiceProcess.ServiceProcessDescriptionAttribute::replaced
IL_0007: ldarg.0
IL_0008: ldarg.1
IL_0009: call instance void [System]System.ComponentModel.DescriptionAttribute::.ctor(string)
IL_000e: ret
} // end of method ServiceProcessDescriptionAttribute::.ctor
I’m sure I just violated something by doing this, but hey, it’s only a couple lines of code! Note that at label IL_0009 it’s calling the base class’s constructor, which looks like this:
.method public hidebysig specialname rtspecialname
instance void .ctor(string description) cil managed
{
// Code size 14 (0xe)
.maxstack 8
IL_0000: ldarg.0
IL_0001: call instance void [mscorlib]System.Attribute::.ctor()
IL_0006: ldarg.0
IL_0007: ldarg.1
IL_0008: stfld string System.ComponentModel.DescriptionAttribute::description
IL_000d: ret
} // end of method DescriptionAttribute::.ctor
So, unless my eyes are deceiving me (which is definitely a possibility), the field called description in DescriptionAttribute should be equal to the constructor’s value. Right? But it’s not - here’s what VS .NET shows in the Locals window:
But, if I subclass DescriptionAttribute myself like this:
public class MyServiceDescriptionAttribute : DescriptionAttribute
{
bool m_Val;
public MyServiceDescriptionAttribute(string Desc) : base(Desc)
{
m_Val = false;
}
public override string Description
{
get
{
return base.Description;
}
}
}
It works just perfectly. And check out the CIL for my constructor:
.method public hidebysig specialname rtspecialname
instance void .ctor(string Desc) cil managed
{
// Code size 15 (0xf)
.maxstack 2
IL_0000: ldarg.0
IL_0001: ldarg.1
IL_0002: call instance void [System]System.ComponentModel.DescriptionAttribute::.ctor(string)
IL_0007: ldarg.0
IL_0008: ldc.i4.0
IL_0009: stfld bool DescriptionAttributeTest.MyServiceDescriptionAttribute::m_Val
IL_000e: ret
} // end of method MyServiceDescriptionAttribute::.ctor
Other than the fact that my code calls the base class’s constructor first and then does the boolean field assignment (the order is flipped in ServiceProcessDescriptionAttribute), nothing looks different to me.
Argh!
Published: 07.22.2002 12:35:00 PM CST