如何：确定数据格式是否存在于数据对象中
更新：2007 年 11 月
下面的示例演示如何使用各种 GetDataPresent 方法重载来查询某个特定的数据格式是否存在于数据对象中。
示例
说明
下面的示例代码使用 GetDataPresent(String) 重载来按说明符字符串查询某个特定的数据格式是否存在。
代码
DataObject dataObject = new DataObject("Some string data to store...");
// Query for the presence of Text data in the data object, by a data format descriptor string.
// In this overload of GetDataPresent, the method will return true both for native data formats
// and when the data can automatically be converted to the specifed format.
// In this case, string data is present natively, so GetDataPresent returns false.
string textData = null;
if (dataObject.GetDataPresent(DataFormats.StringFormat))
{
textData = dataObject.GetData(DataFormats.StringFormat) as string;
}
// In this case, the Text data in the data object can be autoconverted to
// Unicode text, so GetDataPresent returns "true".
byte[] unicodeData = null;
if (dataObject.GetDataPresent(DataFormats.UnicodeText))
{
unicodeData = dataObject.GetData(DataFormats.UnicodeText) as byte[];
}
示例
说明
下面的示例代码使用 GetDataPresent(Type) 重载来按类型查询某个特定的数据格式是否存在。
代码
DataObject dataObject = new DataObject("Some string data to store...");
// Query for the presence of String data in the data object, by type. In this overload
// of GetDataPresent, the method will return true both for native data formats
// and when the data can automatically be converted to the specifed format.
// In this case, the Text data present in the data object can be autoconverted
// to type string (also represented by DataFormats.String), so GetDataPresent returns "true".
string stringData = null;
if (dataObject.GetDataPresent(typeof(string)))
{
stringData = dataObject.GetData(DataFormats.Text) as string;
}
示例
说明
下面的示例代码使用 GetDataPresent(String, Boolean) 重载来按说明符字符串查询数据，并指定如何处理可自动转换的数据格式。
代码
DataObject dataObject = new DataObject("Some string data to store...");
// Query for the presence of Text data in the data object, by data format descriptor string,
// and specifying whether auto-convertible data formats are acceptable.
// In this case, Text data is present natively, so GetDataPresent returns "true".
string textData = null;
if (dataObject.GetDataPresent(DataFormats.Text, false /* Auto-convert? */))
{
textData = dataObject.GetData(DataFormats.Text) as string;
}
// In this case, the Text data in the data object can be autoconverted to
// Unicode text, but it is not available natively, so GetDataPresent returns "false".
byte[] unicodeData = null;
if (dataObject.GetDataPresent(DataFormats.UnicodeText, false /* Auto-convert? */))
{
unicodeData = dataObject.GetData(DataFormats.UnicodeText) as byte[];
}
// In this case, the Text data in the data object can be autoconverted to
// Unicode text, so GetDataPresent returns "true".
if (dataObject.GetDataPresent(DataFormats.UnicodeText, true /* Auto-convert? */))
{
unicodeData = dataObject.GetData(DataFormats.UnicodeText) as byte[];
}