C# 调用C写的DLL时 对应的char* 类型转化为 ref byte

C中代码：

void read( char *filename )
{
    .......
}

C#中代码：

[DllImport("myC.dll", EntryPoint = "read", CharSet = CharSet.Auto)]
public static extern void read(ref byte filename);

调用示例：

string name = @"d:\result\Gaussian_6_0.3.jpg";
            byte[] filename = new byte[100];
            for (int i = 0; i < name.Length; i++)
            {
                filename[i] = (byte)name[i];
            }
            liblept168.read(ref filename[0]);