.NET string字符串的截取、移除、替换、插入

https://www.cnblogs.com/yangwujun/p/5565941.html

在实际开发中经常要用到string的各种截取等操作，在这里总结自己认为经常出现的.NET 字符串的截取、移除、替换、插入操作，方面以后查阅。

前台代码：

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<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="string.aspx.cs" Inherits="demo._string" %>

    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />

</div>
</form>

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后台代码：

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using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

namespace demo
{
public partial class _string : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack == false)
{
string a = "123a4a4b5b6";
TextBox1.Text = a;
}

    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        string b = TextBox1.Text;

        ////截取前两位 123a4a4b5b6   12
        //string c = b.Substring(0, 2);
        //TextBox1.Text = c;

        ////截取后两位  123a4a4b5b6   56
        //string c = b.Substring(b.Length - 2, 2);
        //TextBox1.Text = c;

        ////截取最后一个字符“a”后面的3位字符 123a4a4b5b6     a4b
        //string c = b.Substring(b.LastIndexOf("a"), 3);
        //TextBox1.Text = c;

        ////截取最后一个字符“a”后面所有的字符  123a4a4b5b6     a4b5b6
        //string c = b.Substring(b.LastIndexOf("a"));
        //TextBox1.Text = c;

        ////截取最后一个字符“a”前面所有的字符  123a4a4b5b6    123a4 
        //string c = b.Remove(b.LastIndexOf("a"));
        //TextBox1.Text = c;
        //// 截取最后一个字符“a”前面所有的字符  123a4a4b5b6    123a4 
        //string c = b.Substring(0, b.LastIndexOf("a"));
        //TextBox1.Text = c;

        ////截取最后一个字符“a”前面的3位字符  123a4a4b5b6    123a4    3a4
        //string c = b.Remove(b.LastIndexOf("a"));
        //string d = c.Remove(0, c.Length - 3);
        //TextBox1.Text = d;
        //// 截取最后一个字符“a”前面的3位字符  123a4a4b5b6     3a4    
        //string c = b.Substring(2,b.LastIndexOf("a")-2);
        //TextBox1.Text = c;

        ////截取第一个字符"b"前面所有的字符  123a4a4b5b6  123a4a4
        //int index = b.IndexOf("b");
        //string c = b.Substring(0,index);
        //TextBox1.Text = c;

        ////截取第一个字符"b"前面的3位字符  123a4a4b5b6   4a4
        //string c = b.Substring(0, b.IndexOf("b"));
        //string d = c.Substring(c.Length - 3, 3);
        //TextBox1.Text = d;
        ////截取第一个字符"b"前面的3位字符  123a4a4b5b6   4a4
        //string c = b.Substring(b.IndexOf("b")-3,3);
        //TextBox1.Text = c;

        ////截取第一个字符"b"后面所有的字符  123a4a4b5b6   b5b6
        //int index = b.IndexOf("b");
        //string c = b.Substring(index,b.Length-index);
        //TextBox1.Text = c;
        //////截取第一个字符"b"后面3位字符  123a4a4b5b6   b5b
        //int index = b.IndexOf("b");
        //string c = b.Substring(index, 3);
        //TextBox1.Text = c;








        ////移除从第三位开始的3个字符 123a4a4b5b6   1234b5b6
        //string c = b.Remove(3, 3);
        //TextBox1.Text = c;
        ////移除字符串中的所有字符b;  123a4a4b5b6     123a4a456
        //string c = b.Replace("b", "");
        //TextBox1.Text = c;

        ////移除字符串中的第一个字符a   123a4a4b5b6  1234a4b5b6  
        //int index = b.IndexOf("a",1);
        //b=b.Remove(index, 1);
        //TextBox1.Text = b;

        ////移除字符串中的第一个字符a的后两位   123a4a4b5b6  123a4b5b6  
        //int index = b.IndexOf("a", 1);
        //b = b.Remove(index, 2);
        //TextBox1.Text = b;

        ////移除字符串中的第二个字符a   123a4a4b5b6   123a4b5b6
        //int index = b.IndexOf("a", 2);
        //b = b.Remove(index, 2);
        //TextBox1.Text = b;

        ////移除字符串中的第二个字符a的后两位   123a4a4b5b6    123a4b5b6 
        //int index = b.IndexOf("a", 1);
        //b = b.Remove(index, 2);
        //TextBox1.Text = b;

        ////移除字符串中最后一个字符b   123a4a4b5b6      123a4a4b56 
        //int index = b.LastIndexOf("b");     
        //string c = b.Remove(b.LastIndexOf("b"),1);
        //TextBox1.Text = c;

        ////移除字符串中最后一个字符b的后两位   123a4a4b5b6      123a4a4b5 
        //int index = b.LastIndexOf("b");
        //string c = b.Remove(b.LastIndexOf("b"), 2);
        //TextBox1.Text = c;










        ////替换字符串中所有的字符“a”,为“b”; 123a4a4b5b6     123b4b4b5b6
        //string c = b.Replace("a", "b");
        //TextBox1.Text = c;

        ////替换字符中的第一个字符a为R  123a4a4b5b6    123R4a4b5b6
        //int index = b.IndexOf("a");
        //string c= b.Remove(index, 1).Insert(index, "R");
        //TextBox1.Text = c;

        ////替换字符中的最后一个字符a为R  123a4a4b5b6    123a4R4b5b6
        //int index = b.LastIndexOf("a");
        //string c = b.Remove(index, 1).Insert(index, "R");
        //TextBox1.Text = c;










        ////插入I在第一个a之前  123a4a4b5b6  123Ia4a4b5b6
        //int index = b.IndexOf("a");
        //string c = b.Insert(index, "I");
        //TextBox1.Text = c;

        ////插入I在第一个a之后  123a4a4b5b6   123aI4a4b5b6
        //int index = b.IndexOf("a");
        //string c = b.Insert(index+1, "I");
        //TextBox1.Text = c;

        ////插入I在最后一个a之前  123a4a4b5b6  123a4Ia4b5b6
        //int index = b.LastIndexOf("a");
        //string c = b.Insert(index, "I");
        //TextBox1.Text = c;

        //插入I在最后一个a之后  123a4a4b5b6  123a4aI4b5b6
        int index = b.LastIndexOf("a");
        string c = b.Insert(index + 1, "I");
        TextBox1.Text = c;

    }
}

}
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