The IsPsd method is a static method of the Bitmap class in the Sandbox namespace. It is used to determine whether a given byte array represents a PSD (Photoshop Document) file. This method analyzes the provided byte array to check for the specific signature and structure that identifies a PSD file.

To use the IsPsd method, you need to pass a byte array that you suspect might be a PSD file. The method will return a boolean value indicating whether the byte array is indeed a PSD file.

Example usage:

byte[] fileData = File.ReadAllBytes("path/to/file.psd");
bool isPsd = Bitmap.IsPsd(fileData);
if (isPsd)
{
    // The file is a PSD
}
else
{
    // The file is not a PSD
}