CMFCPropertyGridProperty SetValue 出错处理

对CMFCPropertyGridProperty SetValue时容易报错，这种情况一般是Property和value的类型不匹配造成的。

在创建property的时候，指定了数据类型，如果setvalue时的数据类型与创建时的不一致便会报错。

CMFCPropertyGridProperty的数据类型为_variant_t，它是一个包含了各种数据类型的集合，MSDN中的描述如下：_variant_t对象封装了VARIANT数据类型。 该类管理资源分配和释放，并根据需要对VariantInit和VariantClear进行函数调用。MSDN链接

所以我们在创建property的时候一定要用_variant_t构造函数确定property的数据类型。构造函数的MSDN链接

Remarks

 

• _variant_t( )   Constructs an empty _variant_t object, VT_EMPTY.

• _variant_t( VARIANT& varSrc )   Constructs a _variant_t object from a copy of the VARIANT object. The variant type is retained.

• _variant_t( VARIANT* pVarSrc )   Constructs a _variant_t object from a copy of the VARIANT object. The variant type is retained.

• _variant_t( _variant_t& var_t_Src )   Constructs a _variant_t object from another _variant_t object. The variant type is retained.

• _variant_t( VARIANT& varSrc, bool fCopy )   Constructs a _variant_t object from an existing VARIANT object. If fCopy is false, theVARIANT object is attached to the new object without making a copy.

• _variant_t( short sSrc, VARTYPE vtSrc = VT_I2 )   Constructs a _variant_t object of type VT_I2 or VT_BOOL from a short integer value. Any other VARTYPE results in an E_INVALIDARG error.

• _variant_t( long lSrc, VARTYPE vtSrc = VT_I4 )   Constructs a _variant_t object of type VT_I4, VT_BOOL, or VT_ERROR from a long integer value. Any other VARTYPE results in an E_INVALIDARG error.

• _variant_t( float fltSrc )   Constructs a _variant_t object of type VT_R4 from a float numerical value.

• _variant_t( double dblSrc, VARTYPE vtSrc = VT_R8 )   Constructs a _variant_t object of type VT_R8 or VT_DATE from a double numerical value. Any other VARTYPE results in an E_INVALIDARG error.

• _variant_t( CY& cySrc )   Constructs a _variant_t object of type VT_CY from a CY object.

• _variant_t( _bstr_t& bstrSrc )   Constructs a _variant_t object of type VT_BSTR from a _bstr_t object. A new BSTR is allocated.

• _variant_t( wchar_t *wstrSrc )   Constructs a _variant_t object of type VT_BSTR from a Unicode string. A new BSTR is allocated.

• _variant_t( char* strSrc )   Constructs a _variant_t object of type VT_BSTR from a string. A new BSTR is allocated.

• _variant_t( bool bSrc )   Constructs a _variant_t object of type VT_BOOL from a bool value.

• _variant_t( IUnknown* pIUknownSrc, bool fAddRef = true )   Constructs a _variant_t object of type VT_UNKNOWN from a COM interface pointer. If fAddRef is true, then AddRef is called on the supplied interface pointer to match the call to Release that will occur when the_variant_t object is destroyed. It is up to you to call Release on the supplied interface pointer. If fAddRef is false, this constructor takes ownership of the supplied interface pointer; do not call Release on the supplied interface pointer.

• _variant_t( IDispatch* pDispSrc, bool fAddRef = true )   Constructs a _variant_t object of type VT_DISPATCH from a COM interface pointer. If fAddRef is true, then AddRef is called on the supplied interface pointer to match the call to Release that will occur when the_variant_t object is destroyed. It is up to you to call Release on the supplied interface pointer. If fAddRef is false, this constructor takes ownership of the supplied interface pointer; do not call Release on the supplied interface pointer.

• _variant_t( DECIMAL& decSrc )   Constructs a _variant_t object of type VT_DECIMAL from a DECIMAL value.

• _variant_t( BYTE bSrc )   Constructs a _variant_t object of type VT_UI1 from a BYTE value.

下面是一个标准用法，创建时指定property类型为short，设置数值时指定property类型为short.

// 创建property
CMFCPropertyGridProperty* pProp = new CMFCPropertyGridProperty(_T("透明度"), _variant_t((short), VT_I2), _T("填充透明度0-100"));
    pProp->EnableSpinControl(TRUE, , );
    pGroup3->AddSubItem(pProp);

//设置property数值
sProp->SetValue(_variant_t((short)(sp->mFillTransparency * ), VT_I2));