/// <summary>
/// Determines whether the data object is capable of rendering the data described
/// in the passed clipboard format and storage type(s). Objects attempting a
/// paste or drop operation can call this method before calling GetData
/// to get an indication of whether the operation may be successful
/// </summary>
/// <param name="clipFormat">Name of clipboard format requested</param>
/// <param name="types">type(s) requested</param>
/// <returns>true if the subseqent call to GetData would likely be
/// successful, otherwise false</returns>
public bool QueryGetData(string clipFormat, TYMED types)
{
// populate contents of FORMATETC structure
FORMATETC formatEtc = new FORMATETC();
OleDataObjectHelper.PopulateFORMATETC(clipFormat, types, ref formatEtc);
// try to successfully query for the data
int result = m_dataObject.QueryGetData(ref formatEtc);
// data is available
if (result == HRESULT.S_OK)
{
return(true);
}
// data is not available
else if (result == DV_E.FORMATETC)
{
return(false);
}
// unexpected error
else
{
Marshal.ThrowExceptionForHR(result);
return(false); // keep compiler happy
}
}
/// <summary>
/// Extract the date from within an OleDataObject. Pass in the requested
/// clipboard format and type (or types ORed together) that you want
/// the data in. The method will return an OleStgMedium for the type(s)
/// requested if it is available, otherwise it will return null.
/// If a single type is requested then the return value can be safely
/// cast to the requested OleStgMedium subclasss. If multiple types
/// are requested then the return value will represent the object's
/// preferred storage representation and client code will need to use
/// the 'is' operator to determine what type was returned.
/// </summary>
/// <param name="lindex">Index of item to retreive</param>
/// <param name="clipFormat">Name of clipboard format requested</param>
/// <param name="types">type(s) requested</param>
/// <returns>OleStgMedium instance if format and requested storage type
/// are available, otherwise null</returns>
public OleStgMedium GetData(int lindex, string clipFormat, TYMED types)
{
// populate contents of FORMATETC structure
FORMATETC formatEtc = new FORMATETC();
OleDataObjectHelper.PopulateFORMATETC(lindex, clipFormat, types, ref formatEtc);
// attempt to get the data using the requested format
STGMEDIUM stgMedium = new STGMEDIUM();
if (m_dataObject != null)
{
int result = m_dataObject.GetData(ref formatEtc, ref stgMedium);
// check for errors
if (result != HRESULT.S_OK)
{
// data format not supported (expected error condition)
if (result == DV_E.FORMATETC)
{
return(null);
}
// unexpected error condition
else
{
Marshal.ThrowExceptionForHR(result);
}
}
// return the correct OleStgMedium subclass depending upon the type
switch (stgMedium.tymed)
{
case TYMED.NULL:
return(null);
case TYMED.HGLOBAL:
return(new OleStgMediumHGLOBAL(stgMedium));
case TYMED.FILE:
return(new OleStgMediumFILE(stgMedium));
case TYMED.GDI:
return(new OleStgMediumGDI(stgMedium));
case TYMED.MFPICT:
return(new OleStgMediumMFPICT(stgMedium));
case TYMED.ENHMF:
return(new OleStgMediumENHMF(stgMedium));
case TYMED.ISTREAM:
return(new OleStgMediumISTREAM(stgMedium));
case TYMED.ISTORAGE:
return(new OleStgMediumISTORAGE(stgMedium));
default:
Debug.Assert(false, "Invalid TYMED value");
return(null);
}
}
else
{
return(null);
}
}
/// <summary>
/// Helper function to populate the contents of a FORMATETC structure
/// using the passed clipboard format and type(s).
/// </summary>
/// <param name="clipFormat">Name of clipboard format requested</param>
/// <param name="types">type(s) requested</param>
/// <param name="formatEtc">FORMATETC structure to be populated</param>
public static void PopulateFORMATETC(
string clipFormat, TYMED types, ref FORMATETC formatEtc)
{
OleDataObjectHelper.PopulateFORMATETC(-1, clipFormat, types, ref formatEtc);
}
