Hi Suleyman,You can get MetadataExtension by Its CLSID or name.
private IMetadataHelper GetMetadataExtension()
{
try
{
UID metaDataID = new UIDClass();
//the ProgID
metaDataID.Value = "esriCatalogUI.MetadataExtension";
//or the CLSID
//metaDataID.Value = "{055B2B99-F2C9-11D2-9FC1-00C04F8ED211}"; //ESRI Metadata Extension
IExtension metadataExtension = ArcMap.Application.FindExtensionByCLSID(metaDataID);
return metadataExtension as IMetadataHelper;
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
return null;
}
}