C#对字符串执行字节操作

写两个扩展方法，分别实现“得到字符串的字节长度”和“按字节长度截取字符串”的功能。

public static class Test
{
/// <summary>
/// 按字节长度截取字符串
/// </summary>
/// <param name="str"></param>
/// <param name="num">要截取的字节个数</param>
/// <returns></returns>
public static string SubBytestring(this string str, int num)
{
string strNum = str.Trim();
if (Encoding.Default.GetBytes(strNum).Length <= num)
{
return strNum;
}
byte[] bytes2 = Encoding.Default.GetBytes(str.Substring(0,str.Length<num?str.Length:num));
string strNum1 = Encoding.Default.GetString(bytes2, 0, num);
int len = strNum1.Length;
if (str.Substring(0, len) != strNum1)
{
return Encoding.Default.GetString(bytes2, 0, num - 1);
}
return strNum1;
}
/// <summary>
/// 得到字符串的字节长度
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
public static int ByteLength(this string str)
{
return Encoding.Default.GetBytes(str.Trim()).Length;
}
}

调用：

string str = "a中b华3".SubBytestring(6);
int len = "a中b华3".ByteLength();

参考：http://yandavid.blog.163.com/blog/static/10779084201010182383338/