如何使用c#声明全局函数或方法？

how to declare global function or method using c#?

提问by anonymizer

Can anyone tell me how to declare a global function in c#, similar to what a Moduledoes in VB.net? I need to call a function that can be called in my form1, form2, and form3.

谁能告诉我如何在 c# 中声明一个全局函数，类似于ModuleVB.net 中的 a ？我需要调用一个可以在我的form1、form2和form3中调用的函数。

---

---

i have this code :

我有这个代码：

using System.Data.OleDb;

namespace XYZ
{
    public static class Module
    {
        public static void dbConnection()
        {
            OleDbConnection con = new OleDbConnection();
            con.ConnectionString = "provider= microsoft.jet.oledb.4.0;data source=..\dbCooperative.mdb";
            con.Open();
        }
    }
}

and form1:

和形式1：

using System.Data.OleDb;
using XYZ;

namespace XYZ
{
    public partial class frmReports : Form
    {
        public frm1()
        {
            InitializeComponent();
        }

        private void frm1_Load(object sender, EventArgs e)
        {
            Module.dbConnection();
            OleDbCommand cm = new OleDbCommand("SELECT * FROM table", con);
        }
    }
}

but i has an error: "The name 'con' does not exist in the current context".

但我有一个错误：“当前上下文中不存在名称'con'”。

回答by Kevin Aenmey

You could create a static class.

您可以创建一个静态类。

namespace MyNamespace
{
    public static class MyGlobalClass
    {
        public static void MyMethod() { ... }
    }
}

You would then add the namespace in the usingsection of your calling class to access it. Like this:

然后，您将在using调用类的部分中添加命名空间以访问它。像这样：

using MyNamespace;

public class CallingClass
{
    public  void CallingMethod()
    {
        MyGlobalClass.MyMethod();
    }
}

回答by saluce

You can create a static class (even enclose it in it's own namespace so as not to pollute the main project namespace), then call it from anywhere:

您可以创建一个静态类（甚至将它包含在它自己的命名空间中，以免污染主项目命名空间），然后从任何地方调用它：

namespace SomeNamespace
{
    public static class SomeClass
    {
        public static string SomeMethod() 
        {
            ...
        }
    }
}

Then, in your code, you can call it using:

然后，在您的代码中，您可以使用以下方法调用它：

string x = SomeNamespace.SomeClass.SomeMethod();

Or, you can set up a usingat the top of the code and just reference it without the namespace:

或者，您可以using在代码顶部设置 a并且只引用它而不带命名空间：

using SomeNamespace;
...
string x = SomeClass.SomeMethod();

回答by Alex Nolasco

If you're using C# 6.0 or later, you could use using static.

如果您使用的是 C# 6.0 或更高版本，则可以使用using static.

For example,

例如，

using static ConsoleApplication.Developer;

namespace ConsoleApplication
{
    class Program
    {
        static void Main(string[] args)
        {
            // Global static function, static shorthand really 
            DeveloperIsBorn(firstName: "Foo", lastname: "Bar")
                .MakesAwesomeApp()
                .Retires();
        }
    }
}

namespace ConsoleApplication
{
    class Developer
    {
        public static Developer DeveloperIsBorn(string firstName, string lastname)
        {
            return new Developer();
        }

        public Developer MakesAwesomeApp()
        {
            return this;
        }

        public Developer InsertsRecordsIntoDatabaseForLiving()
        {
            return this;
        }

        public void Retires()
        {
           // Not really
        }        
    }
}

One more example:

再举一个例子：

using static System.Console;

namespace ConsoleApplication7
{
    class Program
    {
        static void Main(string[] args)
        {
            WriteLine("test");
        }
    }
}

回答by Pastor Cortes

@kol is right, there are NO global functions in C#. Take a look at this post MSDN post. I would use layers (I renamed your "Module" class to "TransactionsModule") and It would look like this:

@kol 是对的，C# 中没有全局函数。看看这篇MSDN 帖子。我会使用层（我将你的“模块”类重命名为“事务模块”），它看起来像这样：

using System;
using System.Collections.Generic;
using System.Data.OleDb;

namespace XYZ
{
    public class TransactionsModule
    {
        public List<Person> GetPersons(string query, string connectionString)
        {
            List<Person> dbItems = new List<Person>();

            OleDbConnection conn = new OleDbConnection(connectionString);

            try 
            {
                conn.Open();
                var cmd = new OleDbCommand(query, conn);
                cmd.CommandText = query;

                using (OleDbDataReader reader = cmd.ExecuteReader())
                {
                    Person objPerson = new Person();

                    //These are the columns returned
                    objPerson.Name = Convert.ToString(myReader["Name"]);
                    objPerson.Age = Convert.ToInt32(myReader["Age"]);

                    dbItems.Add(objPerson);
                }
            } 
            catch(OleDbException ex)
            {
                throw ex;
            }
            finally
            {
                conn.Close();
            }
            return dbItems;           
        }


    }

    //This class should be in another Layer, but I placed it here since It's a quick Example
    public class Person
    {
        public string Name { get; set; }
        public int Age { get; set; }
    }
}

All the logic was abstracted to the TransactionsModule class, then you only need to call the Method: GetPersons. Take a look:

所有的逻辑都抽象到了TransactionsModule类中，那么你只需要调用Method：GetPersons。看一看：

using System;
using System.Collections.Generic;
using XYZ.TransactionsModule;

namespace XYZ
{
    public partial class frmReports : Form
    {      
        public frm1()
        {
            InitializeComponent();
            protected TransactionsModule moduleTran;
        }

        private void frm1_Load(object sender, EventArgs e)
        {
            //We initialize the Data Access Layer class
            moduleTran = new TransactionsModule();

            //This ConnectionString should be in your app.config
            string conString = "provider= microsoft.jet.oledb.4.0;data source=..\dbCooperative.mdb";
            string sqlQuery = "SELECT * FROM table";

            List<Person> ItStaff = moduleTran.GetPersons(sqlQuery, conString);
        }
    }
}