c# extension method introductory example

C#Extension method Getting Started Example

Definition of extension method:

##l Must be a static class, static method

##l The first parameter contains the keyword "this", indicating which type this method is assigned to

Code description: The example here is to write a static class, myExtension,an extension methodAdd means that all numbers of type INT will have the ability to call this Add method, provided that # is introduced The namespace of ##MyExtension.

# #Let’s take a look at the usage:

# Code description: What this code does is declare a number of type

int

and assign it as 7, and then When calling the Add method you will see IntelliSense as follows:

You can see that the extension method is marked with a downward arrow. Then just call it, give it any int, because I used the params keyword, it will be automatically parsed into int array, then use the rlt variable to receive it, and when displayed, you will see the result:

# Example 2:

Written a method to extend string, which can standardize English, for example hEllo WORld will be output when passed in, Hello World

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;


namespace wpfLab1
{
    public static class StrExtensenClass
    {
        public static string GetNormalFormat(this string s)
        {
            s = RemoveExtraSpace(s);
            string[] words = s.Split(' ');
            string ret = "";
            foreach (var word in words)
            {
                ret += StrFstChrUpr(word) + " ";
            }
            return ret;
        }


        public static string RemoveExtraSpace(this string s)
        {
            if (s == null || s.Length <= 1)
            {
                return s;
            }


            bool lastChrIsSpace = false;
            string ret = "";
            foreach (var chr in s)
            {
                if (chr == &#39; &#39;)
                {
                    if (lastChrIsSpace)
                    {
                        continue;
                    }
                    else
                    {
                        lastChrIsSpace = true;
                        ret += chr;
                    }
                }
                else
                {
                    ret += chr;
                    lastChrIsSpace = false;
                }


            }
            return ret;
        }


        private static string StrFstChrUpr(string s)
        {
            if (s == null || s.Length < 1)
            {
                return s;
            }
           
            string lowerStr = s.ToLower().Remove(0, 1);
            string upperStr = Char.ToUpper(s[0]).ToString();
            return (upperStr + lowerStr);
        }
    }
}

Use:

##

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using wpfLab1;
namespace wpfLab1
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }


        private void btnHello_Click(object sender, RoutedEventArgs e)
        {
            string s = "hEllo   wOrLd,  hi,   world ,   aa dd  dw   WWdd a ";


            lblHello.Content = s.GetNormalFormat();
            
        }
    }
}

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