文件流转base64字符串

public static string GetBase64Data()
{
string path = @"C: \txt.jpg";
FileStream filestream = new FileStream(path, FileMode.Open);
byte[] bt = new byte[filestream.Length];
//调用read读取方法
filestream.Read(bt, 0, bt.Length);
string base64Str = Convert.ToBase64String(bt);
filestream.Close();
return base64Str;
}