本文实例总结了C#常见应用函数。分享给大家供大家参考，具体如下：
1、页面写CS代码（代码内嵌）
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<%@ Import Namespace="System" %>
<%@ Import Namespace="System.Collections.Generic" %>
<Script runat="server">
public int userId = 0;
protected void Page_Load(object sender, EventArgs e)
{
userId =Convert.ToInt32(Request.QueryString["UserID"]);
Response.Write(userId);
}
</Script>
<%
if (userId > 0){
msg = "欢迎登录!";
}
else {
msg = "未找到用户";
}
%>
<%= this.msg %>
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2、获取时间间隔
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/// <summary>
/// 获取时间间隔（模拟微博发布文章的时间间隔）
/// </summary>
/// <param name="date"></param>
/// <returns></returns>
public string GetDateStr(DateTime date)
{
if (date < DateTime.Now)
{
TimeSpan ts = DateTime.Now - date;
if (ts.TotalHours < 1 && ts.TotalMinutes < 1)
{
return "1分钟前";
}
else if (ts.TotalHours < 1 && ts.TotalMinutes > 0)
{
return Convert.ToInt32(ts.TotalMinutes) + "分钟前";
}
else if (ts.TotalHours < 4)
{
return Convert.ToInt32(ts.TotalHours) + "小时前";
}
else if (DateTime.Now.Date == date.Date)
{
return date.ToString("HH:mm");
}
else
{
return date.ToString("yyyy-MM-dd");
}
}
return date.ToString("yyyy-MM-dd");
}
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3、遍历Url中的参数列表
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/// <summary>
/// 遍历Url中的参数列表
/// </summary>
/// <returns>如:(?userId=43&userType=2)</returns>
public string GetUrlParam()
{
string urlParam = "";
if (Request.QueryString.Count > 0)
{
urlParam = "?";
NameValueCollection keyVals = Request.QueryString;
foreach (string key in keyVals.Keys)
{
urlParam += key + "=" + keyVals[key] + "&";
}
urlParam = urlParam.Substring(0, urlParam.LastIndexOf('&'));
}
return urlParam;
}
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4、清除文本HTML码
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using System.Text.RegularExpressions;
/// <summary>
/// 清除文本HTML码
/// </summary>
public string RemoveHtmlTag(string htmlStr)
{
if (string.IsNullOrEmpty(htmlStr))
return string.Empty;
return Regex.Replace(htmlStr, @"<[^>]*>", "");
}
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5、反射 通过类名创建类实例
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using System.Reflection;
/// <summary>
/// 反射 通过类名创建类实例
/// </summary>
public void ReflecTest()
{
Object objClass = Assembly.GetExecutingAssembly().CreateInstance("MyStudy.BLL.BookInfoBLL"); //参数：类的完全限定名，无需类的后缀名
if (objClass != null)
{
BookInfoBLL bll = (BookInfoBLL)objClass;
}
}
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6、货币类型转换
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/// <summary>
/// 货币
/// </summary>
/// <param name="obj"></param>
/// <returns></returns>
public static string ToMoney(object obj)
{
return String.Format("{0:C}", obj);
}
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7、小数点位数
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//1.小数点位数
string str1 = String.Format("{0:F1}", 56789); //result: 56789.0
string str2 = String.Format("{0:F2}", 56789); //result: 56789.00
string str3 = String.Format("{0:N1}", 56789); //result: 56,789.0
string str4 = String.Format("{0:N2}", 56789); //result: 56,789.00
string str5 = String.Format("{0:N3}", 56789); //result: 56,789.000
string str6 = (56789 / 100.0).ToString("#.##"); //result: 567.89
string str7 = (56789 / 100).ToString("#.##"); //result: 567
//2.保留N位,四舍五入 .
decimal d= decimal.Round(decimal.Parse("0.55555"),2);
//3.保留N位四舍五入
Math.Round(0.55555, 2);
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8、使用TryGetValue改善获取字典值得性能
使用TryGetValue在大量取值时性能比ContainsKey提高一倍。
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Dictionary<int, String> dic = new Dictionary<int, String>();
dic.Add(1,"张三");
dic.Add(2,"李四");
string name = "";
//错误写法，效率底
if (dic.ContainsKey(1))
{
name = dic[1];
Console.WriteLine(name);
}
//正确写法，效率提高一倍
if (dic.TryGetValue(1, out name))
{
Console.WriteLine(name);
}
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希望本文所述对大家C#程序设计有所帮助。