IMetaDataEmit::DefineMethod Method
Creates a definition for a method or global function with the specified signature, and returns a token to that method definition.
HRESULT DefineMethod (
[in] mdTypeDef td,
[in] LPCWSTR szName,
[in] DWORD dwMethodFlags,
[in] PCCOR_SIGNATURE pvSigBlob,
[in] ULONG cbSigBlob,
[in] ULONG ulCodeRVA,
[in] DWORD dwImplFlags,
[out] mdMethodDef *pmd
);
Parameters
td
[in] The mdTypedef token of the parent class or parent interface of the method. Set td to mdTokenNil, if you are defining a global function.szName
[in] The member name in Unicode.dwMethodFlags
[in] A value of the CorMethodAttr enumeration that specifies the attributes of the method or global function.pvSigBlob
[in] The method signature. The signature is persisted as supplied. If you need to specify additional information for any parameters, use the IMetaDataEmit::SetParamProps method.cbSigBlob
[in] The count of bytes in pvSigBlob.ulCodeRVA
[in] The address of the code.dwImplFlags
[in] A value of the CorMethodImpl enumeration that specifies the implementation features of the method.pmd
[out] The member token.
Remarks
The metadata API guarantees to persist methods in the same order as the caller emits them for a given enclosing class or interface, which is specified in the td parameter.
Additional information regarding the use of DefineMethod and particular parameter settings is given below.
Slots in the V-table
The runtime uses method definitions to set up v-table slots. In the case where one or more slots need to be skipped, such as to preserve parity with a COM interface layout, a dummy method is defined to take up the slot or slots in the v-table; set the dwMethodFlags to the mdRTSpecialName value of the CorMethodAttr enumeration and specify the name as:
_VtblGap<SequenceNumber><_CountOfSlots>
where SequenceNumber is the sequence number of the method and CountOfSlots is the number of slots to skip in the v-table. If CountOfSlots is omitted, 1 is assumed. These dummy methods are not callable from either managed or unmanaged code and any attempt to call them, from either managed or unmanaged code, generates an exception. Their only purpose is to take up space in the v-table that the runtime generates for COM integration.
Duplicate Methods
You should not define duplicate methods. That is, you should not call DefineMethod with a duplicate set of values in the td, wzName, and pvSig parameters. (These three parameters together uniquely define the method.). However, you can use a duplicate triple provided that, for one of the method definitions, you set the mdPrivateScope bit in the dwMethodFlags parameter. (The mdPrivateScope bit means that the compiler will not emit a reference to this method definition.)
Method Implementation Information
Information about the method implementation is often not known at the time the method is declared. Therefore, you do not need to pass values in the ulCodeRVA and dwImplFlags parameters when calling DefineMethod. The values can be supplied later through IMetaDataEmit::SetMethodImplFlags or IMetaDataEmit::SetRVA, as appropriate.
In some situations, such as platform invocation (PInvoke) or COM interop scenarios, the method body will not be supplied, and ulCodeRVA should be set to zero. In these situations, the method should not be tagged as abstract, because the runtime will locate the implementation.
Defining a Method for PInvoke
For each unmanaged function to be called through PInvoke, you must define a managed method that represents the target unmanaged function. To define the managed method, use DefineMethod with some of the parameters set to certain values, depending on the way in which PInvoke is used:
True PInvoke - involves invocation of an external unmanaged method that resides in an unmanaged DLL.
Local PInvoke - involves invocation of a native unmanaged method that is embedded in the current managed module.
The parameter settings are given in the following table.
Parameter |
Values for true PInvoke |
Values for local PInvoke |
|---|---|---|
dwMethodFlags |
Set mdStatic; clear mdSynchronized and mdAbstract. |
|
pvSigBlob |
A valid common language runtime (CLR) method signature with parameters that are valid managed types. |
A valid CLR method signature with parameters that are valid managed types. |
ulCodeRVA |
0 |
|
dwImplFlags |
Set miCil and miManaged. |
Set miNative and miUnmanaged. |
Requirements
Platforms: Windows 2000, Windows XP, Windows Server 2003 family
Header: Cor.h
Library: Used as a resource in MSCorEE.dll
.NET Framework Version: 2.0, 1.1, 1.0