/// <summary>
/// Retrieves a string associated with a key.
/// </summary>
/// <param name="attributes">A valid IMFAttributes instance.</param>
/// <param name="guidKey">Guid that identifies which value to retrieve.</param>
/// <param name="value">Receives the string.</param>
/// <returns>If this function succeeds, it returns the S_OK member. Otherwise, it returns another HResult's member that describe the error.</returns>
public static HResult GetString(this IMFAttributes attributes, Guid guidKey, out string value)
{
if (attributes == null)
{
throw new ArgumentNullException("attributes");
}
value = null;
int stringLength;
HResult hr = attributes.GetStringLength(guidKey, out stringLength);
if (hr.Failed())
{
return(hr);
}
StringBuilder sb = new StringBuilder(stringLength + 1);
hr = attributes.GetString(guidKey, sb, sb.Capacity, out stringLength);
if (hr.Failed())
{
return(hr);
}
value = sb.ToString();
return(hr);
}
public static string GetString(this IMFAttributes obj, Guid key, string defaultValue = null)
{
if (obj == null)
{
throw new ArgumentNullException(nameof(obj));
}
if (obj.GetStringLength(key, out var length).IsError)
{
return(defaultValue);
}
var s = new string('\0', (int)length);
length++;
obj.GetString(key, s, length, ref length).ThrowOnError();
return(s);
}
public HResult GetStringLength(Guid guidKey, out int pcchLength)
{
return(m_Attribs.GetStringLength(guidKey, out pcchLength));
}