string content = "木子屋(http://www.mzwu.com/)";

//2字节存储
using (FileStream fs = File.Create(@"c:\test.txt"))
{
    using (BinaryWriter writer = new BinaryWriter(fs))
    {
        for (int i = 0; i < content.Length; i++)
            writer.Write((short)content[i]);
    }
}

//4字节存储
using (FileStream fs = File.Create(@"c:\test2.txt"))
{
    using (BinaryWriter writer = new BinaryWriter(fs))
    {
        for (int i = 0; i < content.Length; i++)
            writer.Write((int)content[i]);
    }
}

//8字节存储
using (FileStream fs = File.Create(@"c:\test3.txt"))
{
    using (BinaryWriter writer = new BinaryWriter(fs))
    {
        for (int i = 0; i < content.Length; i++)
            writer.Write((long)content[i]);
    }
}

byte[] b;

//2字节,0x28 0x67
b = BitConverter.GetBytes((short)'木');
for (int i = 0; i < b.Length; i++)
    Console.Write(b[i] + " ");
Console.WriteLine(BitConverter.ToChar(b, 0));

//4字节,0x28 0x67 0 0
b = BitConverter.GetBytes((int)'木');
for (int i = 0; i < b.Length; i++)
    Console.Write(b[i] + " ");
Console.WriteLine(BitConverter.ToChar(b, 0));//注意,ToChar只取2个字节进行转换

//8字节,0x28 0x67 0 0 0 0 0 0
b = BitConverter.GetBytes((long)'木');
for (int i = 0; i < b.Length; i++)
    Console.Write(b[i] + " ");
Console.WriteLine(BitConverter.ToChar(b, 0));