本文介绍了一系列实用的字符串处理方法，包括获取文件扩展名、截取指定长度的字符串、获取电子邮件主机名等。此外，还提供了生成分页链接的示例代码，并展示了如何判断文件流是否为UTF8编码。
/// <summary>
/// 获取指定文件的扩展名 例: .txt
/// </summary>
/// <param name="fileName">指定文件名</param>
/// <returns>扩展名</returns>
public static string GetFileExtName(string fileName)
{
if (GF_IsOk.IsStrNullOrEmpty(fileName) || fileName.IndexOf('.') <= 0)
return "";
fileName = fileName.ToLower().Trim();
return fileName.Substring(fileName.LastIndexOf('.'), fileName.Length - fileName.LastIndexOf('.'));
}
public static string GetSubString(string p_SrcString, int p_Length, string p_TailString)
{
return GetSubString(p_SrcString, 0, p_Length, p_TailString);
}
public static string GetUnicodeSubString(string str, int len, string p_TailString)
{
string result = string.Empty;// 最终返回的结果
int byteLen = System.Text.Encoding.Default.GetByteCount(str);// 单字节字符长度
int charLen = str.Length;// 把字符平等对待时的字符串长度
int byteCount = 0;// 记录读取进度
int pos = 0;// 记录截取位置
if (byteLen > len)
{
for (int i = 0; i < charLen; i++)
{
if (Convert.ToInt32(str.ToCharArray()[i]) > 255)// 按中文字符计算加2
byteCount += 2;
else// 按英文字符计算加1
byteCount += 1;
if (byteCount > len)// 超出时只记下上一个有效位置
{
pos = i;
break;
}
else if (byteCount == len)// 记下当前位置
{
pos = i + 1;
break;
}
}
if (pos >= 0)
result = str.Substring(0, pos) + p_TailString;
}
else
result = str;
return result;
}
/// <summary>
/// 取指定长度的字符串
/// </summary>
/// <param name="p_SrcString">要检查的字符串</param>
/// <param name="p_StartIndex">起始位置</param>
/// <param name="p_Length">指定长度</param>
/// <param name="p_TailString">用于替换的字符串</param>
/// <returns>截取后的字符串</returns>
public static string GetSubString(string p_SrcString, int p_StartIndex, int p_Length, string p_TailString)
{
string myResult = p_SrcString;
Byte[] bComments = Encoding.UTF8.GetBytes(p_SrcString);
foreach (char c in Encoding.UTF8.GetChars(bComments))
{ //当是日文或韩文时(注:中文的范围:\u4e00 - \u9fa5, 日文在\u0800 - \u4e00, 韩文为\xAC00-\xD7A3)
if ((c > '\u0800' && c < '\u4e00') || (c > '\xAC00' && c < '\xD7A3'))
{
//if (System.Text.RegularExpressions.Regex.IsMatch(p_SrcString, "[\u0800-\u4e00]+") || System.Text.RegularExpressions.Regex.IsMatch(p_SrcString, "[\xAC00-\xD7A3]+"))
//当截取的起始位置超出字段串长度时
if (p_StartIndex >= p_SrcString.Length)
return "";
else
return p_SrcString.Substring(p_StartIndex,
((p_Length + p_StartIndex) > p_SrcString.Length) ? (p_SrcString.Length - p_StartIndex) : p_Length);
}
}
if (p_Length >= 0)
{
byte[] bsSrcString = Encoding.Default.GetBytes(p_SrcString);
//当字符串长度大于起始位置
if (bsSrcString.Length > p_StartIndex)
{
int p_EndIndex = bsSrcString.Length;
//当要截取的长度在字符串的有效长度范围内
if (bsSrcString.Length > (p_StartIndex + p_Length))
{
p_EndIndex = p_Length + p_StartIndex;
}
else
{ //当不在有效范围内时,只取到字符串的结尾
p_Length = bsSrcString.Length - p_StartIndex;
p_TailString = "";
}
int nRealLength = p_Length;
int[] anResultFlag = new int[p_Length];
byte[] bsResult = null;
int nFlag = 0;
for (int i = p_StartIndex; i < p_EndIndex; i++)
{
if (bsSrcString[i] > 127)
{
nFlag++;
if (nFlag == 3)
nFlag = 1;
}
else
nFlag = 0;
anResultFlag[i] = nFlag;
}
if ((bsSrcString[p_EndIndex - 1] > 127) && (anResultFlag[p_Length - 1] == 1))
nRealLength = p_Length + 1;
bsResult = new byte[nRealLength];
Array.Copy(bsSrcString, p_StartIndex, bsResult, 0, nRealLength);
myResult = Encoding.Default.GetString(bsResult);
myResult = myResult + p_TailString;
}
}
return myResult;
}
/// <summary>
/// 获取Email HostName 例 liyangfd@gmail.com 获取出来时@gmail.com
/// </summary>
/// <param name="strEmail"></param>
/// <returns></returns>
public static string GetEmailHostName(string strEmail)
{
if (strEmail.IndexOf("@") < 0)
{
return "";
}
return strEmail.Substring(strEmail.LastIndexOf("@")).ToLower();
}
/// <summary>
/// 返回URL中结尾的文件名
/// </summary>
public static string GetFilename(string url)
{
if (url == null)
{
return "";
}
string[] strs1 = url.Split(new char[] { '/' });
return strs1[strs1.Length - 1].Split(new char[] { '?' })[0];
}
/// <summary>
/// 根据阿拉伯数字返回月份的名称(可更改为某种语言)
/// </summary>
public static string[] Monthes
{
get
{
return new string[] { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };
}
}
/// <summary>
/// 获得伪静态页码显示链接
/// </summary>
/// <param name="curPage">当前页数</param>
/// <param name="countPage">总页数</param>
/// <param name="url">超级链接地址</param>
/// <param name="extendPage">周边页码显示个数上限</param>
/// <returns>页码html</returns>
public static string GetStaticPageNumbers(int curPage, int countPage, string url, string expname, int extendPage)
{
return GetStaticPageNumbers(curPage, countPage, url, expname, extendPage, 0);
}
/// <summary>
/// 获得伪静态页码显示链接
/// </summary>
/// <param name="curPage">当前页数</param>
/// <param name="countPage">总页数</param>
/// <param name="url">超级链接地址</param>
/// <param name="extendPage">周边页码显示个数上限</param>
/// <param name="forumrewrite">当前版块是否使用URL重写</param>
/// <returns>页码html</returns>
public static string GetStaticPageNumbers(int curPage, int countPage, string url, string expname, int extendPage, int forumrewrite)
{
int startPage = 1;
int endPage = 1;
string t1 = "<a href=\"" + url + "-1" + expname + "\">«</a>";
string t2 = "<a href=\"" + url + "-" + countPage + expname + "\">»</a>";
if (forumrewrite == 1)
{
t1 = "<a href=\"" + url + "/1/list" + expname + "\">«</a>";
t2 = "<a href=\"" + url + "/" + countPage + "/list" + expname + "\">»</a>";
}
if (forumrewrite == 2)
{
t1 = "<a href=\"" + url + "/\">«</a>";
t2 = "<a href=\"" + url + "/" + countPage + "/\">»</a>";
}
if (countPage < 1) countPage = 1;
if (extendPage < 3) extendPage = 2;
if (countPage > extendPage)
{
if (curPage - (extendPage / 2) > 0)
{
if (curPage + (extendPage / 2) < countPage)
{
startPage = curPage - (extendPage / 2);
endPage = startPage + extendPage - 1;
}
else
{
endPage = countPage;
startPage = endPage - extendPage + 1;
t2 = "";
}
}
else
{
endPage = extendPage;
t1 = "";
}
}
else
{
startPage = 1;
endPage = countPage;
t1 = "";
t2 = "";
}
StringBuilder s = new StringBuilder("");
s.Append(t1);
for (int i = startPage; i <= endPage; i++)
{
if (i == curPage)
{
s.Append("<span>");
s.Append(i);
s.Append("</span>");
}
else
{
s.Append("<a href=\"");
if (forumrewrite == 1)
{
s.Append(url);
if (i != 1)
{
s.Append("/");
s.Append(i);
}
s.Append("/list");
s.Append(expname);
}
else if (forumrewrite == 2)
{
s.Append(url);
s.Append("/");
if (i != 1)
{
s.Append(i);
s.Append("/");
}
}
else
{
s.Append(url);
if (i != 1)
{
s.Append("-");
s.Append(i);
}
s.Append(expname);
}
s.Append("\">");
s.Append(i);
s.Append("</a>");
}
}
s.Append(t2);
return s.ToString();
}
/// <summary>
/// 获得帖子的伪静态页码显示链接
/// </summary>
/// <param name="expname"></param>
/// <param name="countPage">总页数</param>
/// <param name="url">超级链接地址</param>
/// <param name="extendPage">周边页码显示个数上限</param>
/// <returns>页码html</returns>
public static string GetPostPageNumbers(int countPage, string url, string expname, int extendPage)
{
int startPage = 1;
int endPage = 1;
int curPage = 1;
string t1 = "<a href=\"" + url + "-1" + expname + "\">«</a>";
string t2 = "<a href=\"" + url + "-" + countPage + expname + "\">»</a>";
if (countPage < 1) countPage = 1;
if (extendPage < 3) extendPage = 2;
if (countPage > extendPage)
{
if (curPage - (extendPage / 2) > 0)
{
if (curPage + (extendPage / 2) < countPage)
{
startPage = curPage - (extendPage / 2);
endPage = startPage + extendPage - 1;
}
else
{
endPage = countPage;
startPage = endPage - extendPage + 1;
t2 = "";
}
}
else
{
endPage = extendPage;
t1 = "";
}
}
else
{
startPage = 1;
endPage = countPage;
t1 = "";
t2 = "";
}
StringBuilder s = new StringBuilder("");
s.Append(t1);
for (int i = startPage; i <= endPage; i++)
{
s.Append("<a href=\"");
s.Append(url);
s.Append("-");
s.Append(i);
s.Append(expname);
s.Append("\">");
s.Append(i);
s.Append("</a>");
}
s.Append(t2);
return s.ToString();
}
/// <summary>
/// 获得页码显示链接
/// </summary>
/// <param name="curPage">当前页数</param>
/// <param name="countPage">总页数</param>
/// <param name="url">超级链接地址</param>
/// <param name="extendPage">周边页码显示个数上限</param>
/// <returns>页码html</returns>
public static string GetPageNumbers(int curPage, int countPage, string url, int extendPage)
{
return GetPageNumbers(curPage, countPage, url, extendPage, "page");
}
/// <summary>
/// 获得页码显示链接
/// </summary>
/// <param name="curPage">当前页数</param>
/// <param name="countPage">总页数</param>
/// <param name="url">超级链接地址</param>
/// <param name="extendPage">周边页码显示个数上限</param>
/// <param name="pagetag">页码标记</param>
/// <returns>页码html</returns>
public static string GetPageNumbers(int curPage, int countPage, string url, int extendPage, string pagetag)
{
return GetPageNumbers(curPage, countPage, url, extendPage, pagetag, null);
}
/// <summary>
/// 获得页码显示链接
/// </summary>
/// <param name="curPage">当前页数</param>
/// <param name="countPage">总页数</param>
/// <param name="url">超级链接地址</param>
/// <param name="extendPage">周边页码显示个数上限</param>
/// <param name="pagetag">页码标记</param>
/// <param name="anchor">锚点</param>
/// <returns>页码html</returns>
public static string GetPageNumbers(int curPage, int countPage, string url, int extendPage, string pagetag, string anchor)
{
if (pagetag == "")
pagetag = "page";
int startPage = 1;
int endPage = 1;
if (url.IndexOf("?") > 0)
url = url + "&";
else
url = url + "?";
string t1 = "<a href=\"" + url + "&" + pagetag + "=1";
string t2 = "<a href=\"" + url + "&" + pagetag + "=" + countPage;
if (anchor != null)
{
t1 += anchor;
t2 += anchor;
}
t1 += "\">«</a>";
t2 += "\">»</a>";
if (countPage < 1)
countPage = 1;
if (extendPage < 3)
extendPage = 2;
if (countPage > extendPage)
{
if (curPage - (extendPage / 2) > 0)
{
if (curPage + (extendPage / 2) < countPage)
{
startPage = curPage - (extendPage / 2);
endPage = startPage + extendPage - 1;
}
else
{
endPage = countPage;
startPage = endPage - extendPage + 1;
t2 = "";
}
}
else
{
endPage = extendPage;
t1 = "";
}
}
else
{
startPage = 1;
endPage = countPage;
t1 = "";
t2 = "";
}
StringBuilder s = new StringBuilder("");
s.Append(t1);
for (int i = startPage; i <= endPage; i++)
{
if (i == curPage)
{
s.Append("<span>");
s.Append(i);
s.Append("</span>");
}
else
{
s.Append("<a href=\"");
s.Append(url);
s.Append(pagetag);
s.Append("=");
s.Append(i);
if (anchor != null)
{
s.Append(anchor);
}
s.Append("\">");
s.Append(i);
s.Append("</a>");
}
}
s.Append(t2);
return s.ToString();
}
/// <summary>
/// 判断文件流是否为UTF8字符集
/// </summary>
/// <param name="sbInputStream">文件流</param>
/// <returns>判断结果</returns>
private static bool IsUTF8(FileStream sbInputStream)
{
int i;
byte cOctets; // octets to go in this UTF-8 encoded character
byte chr;
bool bAllAscii = true;
long iLen = sbInputStream.Length;
cOctets = 0;
for (i = 0; i < iLen; i++)
{
chr = (byte)sbInputStream.ReadByte();
if ((chr & 0x80) != 0) bAllAscii = false;
if (cOctets == 0)
{
if (chr >= 0x80)
{
do
{
chr <<= 1;
cOctets++;
}
while ((chr & 0x80) != 0);
cOctets--;
if (cOctets == 0)
return false;
}
}
else
{
if ((chr & 0xC0) != 0x80)
return false;
cOctets--;
}
}
if (cOctets > 0)
return false;
if (bAllAscii)
return false;
return true;
}
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