/// <summary>
/// AppendFileRangeToBody() is used to append part or
/// all of a file, to be uploaded, to the request body. A content-length
/// request header will be automatically generated.
/// </summary>
/// <param name="fileRef">A <code>FileRef</code> containing the file
/// reference.</param>
/// <param name="startOffset">An optional starting point offset within the
/// file.</param>
/// <param name="length">An optional number of bytes of the file to
/// be included. If the value is -1, then the sub-range to upload extends
/// to the end of the file.</param>
/// <param name="utcExpectedLastModifiedTime">An optional last
/// modified time stamp used to validate that the file was not modified since
/// the given time before it was uploaded. The upload will fail with an error
/// code of <code>ErrorFilechanged</code> if the file has been modified
/// since the given time. If utcExpectedLastModifiedTime is null, then no
/// validation is performed.</param>
/// <returns>true if successful, false if any of the parameters are invalid.</returns>
public bool AppendFileRangeToBody(FileRef fileRef,
long startOffset,
long length,
DateTime?utcExpectedLastModifiedTime = null)
=> PPBURLRequestInfo.AppendFileToBody(this,
fileRef,
startOffset,
length,
(utcExpectedLastModifiedTime.HasValue) ? PepperSharpUtils.ConvertToPepperTimestamp(utcExpectedLastModifiedTime.Value) : 0) == PPBool.True;
