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  • C#中调用API

     

    介绍
    API( Application Programming Interface ),我想大家不会陌生,它是我们Windows编程的常客,虽然基于.Net平台的C#有了强大的类库,但是,我们还是不能否认API在Windows编程中的重要性.大多数的编程语言都支持API编程,而.Net平台中的MFC(Microsoft Foundation Class Library)构架本身就封装了大部分的API.

        做为程序员,我们需要了解API从字面上了解便是编程接口,因此,做为开发者,需要了解的只是API的使用方法.

    API根据操作系统、处理器及功能性的不同而拥有很多不同的类型.     操作系统特用的API:

        每种操作系统都有许多通用的API以及一些特用的API,这些特用的API只能在当前操作系统中执行.

        例如:

    Windows NT 支持 MS-DOS, Win16, Win32, POSIX ( Portable Operating System Interface ), OS/2 console API; 而 Windows 95 支持 MS-DOS, Win16 以及 Win32 APIs.

    Win16 & Win32 API:

    Win16是为十六位处理器开发的,早期的操作系统均支持.

    Win32则是为32位处理器开发.它可移植性强,被大部分的处理器所支持.

    Win32 API在库名后有一个”32”后缀.比如KERNEL32,USER32等.

        所有API在下面3个库中得以运行:

    Kernel
    User
    GDI

    1. KERNEL

        他的库名为 KERNEL32.DLL, 他主要用于产生与操作系统之间的关联:

        程序加载
         上下文选择.
         文件输入输出.
         内存管理.
         例如: GlobalMemoryStatus 函数就包括当前物理内存及虚拟内存的使用信息.

    2. USER

        这个类库在Win32中名叫 USER32.DLL.

        它允许管理全部的用户接口,比如:

        窗口
         菜单
         对话框
         图标等.,
         例如: DrawIcon 函数将在指定的设备关联上“画”出图标或者鼠标.

    3. GDI ( Graphical Device Interface )

        它在Win32中的库名为:GDI32.dll,它是图形输出库.使用GDI Windows“画”出窗口、菜单以及对话框等:

        它能创建图形输出.
         它也能保存图形文件.
         例如: CreateBitmap 函数就能通过指定的长、宽、颜色创建一个位图.
    C# 中操作API :

         作为初学者来说,在C#中使用API确是一件令人头疼的问题.在使用API之间你必须知道如何在C#中使用结构、类型转换、安全/不安全代码,可控/不可控代码等许多知识.

         一切从简单开始,复杂的大家一时不能接受.我们就从实现一个简单的MessageBox开始.首先打开VS.Net ,创建一个新的C#工程,并添加一个Button按钮.当这个按钮被点击,则显示一个MessageBox对话框.

         即然我们需要引用外来库,所以必须导入一个Namespace:


    using System.Runtime.InteropServices; 

         接着添加下面的代码来声明一个API:

    [DllImport( "User32.dll" )]

    public static extern int MessageBox( int h, string m, string c, int type ); 

         此处DllImport属性被用来从不可控代码中调用一方法.”User32.dll”则设定了类库名.DllImport属性指定dll的位置,这个dll中包括调用的外部方法.Static修饰符则声明一个静态元素,而这个元素属于类型本身而不是上面指定的对象.extern则表示这个方法将在工程外部执行,使用DllImport导入的方法必须使用extern修饰符.

    MessageBox 则是函数名,拥有4个参数,其返回值为数字.

         大多数的API都能传递并返回值.

         添中Click点击事件代码:

    protected void button1_Click( object sender, System.EventArgs e )

    {
       
        MessageBox ( 0,"API Message Box","API Demo",0 );
       


         编译并运行这个程序,当你点击按钮后,你将会看到对话框,这便是你使用的API函数.

         使用结构体

         操作带有结构体的API比使用简单的API要复杂的多.但是一旦你掌握了API的过程,那个整个API世界将在你的掌握之中.

         下面的例子中我们将使用GetSystemInfo API 来获取整个系统的信息.

         第一步还是打开C#建立一个Form工程,同样的添中一个Button按钮,在代码窗中输入下面的代码,导入Namespace:

    using System.Runtime.InteropServices; 

         声明一个结构体,它将做为GetSystemInfo的一个参数:


    [StructLayout( LayoutKind.Sequential )]

    public struct SYSTEM_INFO {
       
        public uint dwOemId;
       
        public uint dwPageSize;
       
        public uint lpMinimumApplicationAddress;
       
        public uint lpMaximumApplicationAddress;
       
        public uint dwActiveProcessorMask;
       
        public uint dwNumberOfProcessors;
       
        public uint dwProcessorType;
       
        public uint dwAllocationGranularity;
       
        public uint dwProcessorLevel;
       
        public uint dwProcessorRevision;
       


    声明API函数:


    [DllImport( "kernel32" )]

    static extern void GetSystemInfo( ref SYSTEM_INFO pSI ); 

         添加下面的代码至按钮的点击事件处理中:

         首先创建一个SYSTEM_INFO结构体,并将其传递给GetSystemInfo函数.

    protected void button1_Click ( object sender, System.EventArgs e )

    {
       
        try
       
        {
           
            SYSTEM_INFO pSI = new SYSTEM_INFO( );
           
            GetSystemInfo( ref pSI );
           
            //
           
            //
           
            // 
           
         一旦你接收到返回的结构体,那么就可以以返回的参数来执行操作了.
           
           
            e.g.listBox1.InsertItem ( 0,pSI.dwActiveProcessorMask.ToString( ) );:
           
            //
           
            //
           
            //
           
        }
       
        catch( Exception er )
       
        {
           
            MessageBox.Show ( er.Message );
           
        }
       


    调用API全部代码

    //Created By Ajit Mungale

    //程序补充 飞刀

    namespace UsingAPI

    {
       
        using System;
       
        using System.Drawing;
       
        using System.Collections;
       
        using System.ComponentModel;
       
        using System.WinForms;
       
        using System.Data;
       
        using System.Runtime.InteropServices;
       
        //Struct 收集系统信息
       
        [StructLayout( LayoutKind.Sequential )]
       
        public struct SYSTEM_INFO {
           
            public uint dwOemId;
           
            public uint dwPageSize;
           
            public uint lpMinimumApplicationAddress;
           
            public uint lpMaximumApplicationAddress;
           
            public uint dwActiveProcessorMask;
           
            public uint dwNumberOfProcessors;
           
            public uint dwProcessorType;
           
            public uint dwAllocationGranularity;
           
            public uint dwProcessorLevel;
           
            public uint dwProcessorRevision;
           
        }
       
        //struct 收集内存情况
       
        [StructLayout( LayoutKind.Sequential )]
       
        public struct MEMORYSTATUS
       
        {
           
            public uint dwLength;
           
            public uint dwMemoryLoad;
           
            public uint dwTotalPhys;
           
            public uint dwAvailPhys;
           
            public uint dwTotalPageFile;
           
            public uint dwAvailPageFile;
           
            public uint dwTotalVirtual;
           
            public uint dwAvailVirtual;
           
        }
       
        public class Form1 : System.WinForms.Form
       
        {
           
            private System.ComponentModel.Container components;
           
            private System.WinForms.MenuItem menuAbout;
           
            private System.WinForms.MainMenu mainMenu1;
           
            private System.WinForms.ListBox listBox1;
           
            private System.WinForms.Button button1;
           
            //获取系统信息
           
            [DllImport( "kernel32" )]
           
            static extern void GetSystemInfo( ref SYSTEM_INFO pSI );
           
            //获取内存信息
           
            [DllImport( "kernel32" )]
           
            static extern void GlobalMemoryStatus( ref MEMORYSTATUS buf );
           
            //处理器类型
           
            public const int PROCESSOR_INTEL_386 = 386;
           
            public const int PROCESSOR_INTEL_486 = 486;
           
            public const int PROCESSOR_INTEL_PENTIUM = 586;
           
            public const int PROCESSOR_MIPS_R4000 = 4000;
           
            public const int PROCESSOR_ALPHA_21064 = 21064;
           
            public Form1( )
           
            {
               
                InitializeComponent( );
               
            }
           
            public override void Dispose( )
           
            {
               
                base.Dispose( );
               
                components.Dispose( );
               
            }
           
            private void InitializeComponent( )
           
            {
               
                this.components = new System.ComponentModel.Container ( );
               
                this.mainMenu1 = new System.WinForms.MainMenu ( );
               
                this.button1 = new System.WinForms.Button ( );
               
                this.listBox1 = new System.WinForms.ListBox ( );
               
                this.menuAbout = new System.WinForms.MenuItem ( );
               
                mainMenu1.MenuItems.All = new System.WinForms.MenuItem[1] {this.menuAbout};
               
                button1.Location = new System.Drawing.Point ( 148, 168 );
               
                button1.Size = new System.Drawing.Size ( 112, 32 );
               
                button1.TabIndex = 0;
               
                button1.Text = "&Get Info";
               
                button1.Click += new System.EventHandler ( this.button1_Click );
               
                listBox1.Location = new System.Drawing.Point ( 20, 8 );
               
                listBox1.Size = new System.Drawing.Size ( 368, 147 );
               
                listBox1.TabIndex = 1;
               
                menuAbout.Text = "&About";
               
                menuAbout.Index = 0;
               
                menuAbout.Click += new System.EventHandler ( this.menuAbout_Click );
               
                this.Text = "System Information - Using API";
               
                this.MaximizeBox = false;
               
                this.AutoScaleBaseSize = new System.Drawing.Size ( 5, 13 );
               
                this.MinimizeBox = false;
               
                this.Menu = this.mainMenu1;
               
                this.ClientSize = new System.Drawing.Size ( 408, 213 );
               
                this.Controls.Add ( this.listBox1 );
               
                this.Controls.Add ( this.button1 );
               
            }
           
            protected void menuAbout_Click ( object sender, System.EventArgs e )
           
            {
               
                Form abt=new about( ) ;
               
                abt.ShowDialog( );
               
            }
           
            protected void button1_Click ( object sender, System.EventArgs e )
           
            {
               
                try
               
                {
                   
                    SYSTEM_INFO pSI = new SYSTEM_INFO( );
                   
                    GetSystemInfo( ref pSI );
                   
                    string CPUType;
                   
                    switch ( pSI.dwProcessorType )
                   
                    {
                       
                        case PROCESSOR_INTEL_386 :
                       
                        CPUType= "Intel 386";
                       
                        break;
                       
                        case PROCESSOR_INTEL_486 :
                       
                        CPUType = "Intel 486" ;
                       
                        break;
                       
                        case PROCESSOR_INTEL_PENTIUM :
                       
                        CPUType = "Intel Pentium";
                       
                        break;
                       
                        case PROCESSOR_MIPS_R4000 :
                       
                        CPUType = "MIPS R4000";
                       
                        break;
                       
                        case PROCESSOR_ALPHA_21064 :
                       
                        CPUType = "DEC Alpha 21064";
                       
                        break;
                       
                        default :
                       
                        CPUType = "( unknown )";
                       
                    }
                   
                    listBox1.InsertItem ( 0,"Active Processor Mask :"+pSI.dwActiveProcessorMask.ToString( ) );
                   
                    listBox1.InsertItem ( 1,"Allocation Granularity :"+pSI.dwAllocationGranularity.ToString( ) );
                   
                    listBox1.InsertItem ( 2,"Number Of Processors :"+pSI.dwNumberOfProcessors.ToString( ) );
                   
                    listBox1.InsertItem ( 3,"OEM ID :"+pSI.dwOemId.ToString( ) );
                   
                    listBox1.InsertItem ( 4,"Page Size:"+pSI.dwPageSize.ToString( ) );
                   
                    listBox1.InsertItem ( 5,"Processor Level Value:"+pSI.dwProcessorLevel.ToString( ) );
                   
                    listBox1.InsertItem ( 6,"Processor Revision:"+ pSI.dwProcessorRevision.ToString( ) );
                   
                    listBox1.InsertItem ( 7,"CPU type:"+CPUType );
                   
                    listBox1.InsertItem ( 8,"Maximum Application Address: "+pSI.lpMaximumApplicationAddress.ToString( ) );
                   
                    listBox1.InsertItem ( 9,"Minimum Application Address:" +pSI.lpMinimumApplicationAddress.ToString( ) );
                   
                    /************** 从 GlobalMemoryStatus 获取返回值****************/
                   
                    MEMORYSTATUS memSt = new MEMORYSTATUS ( );
                    GlobalMemoryStatus ( ref memSt );
                   
                    listBox1.InsertItem( 10,"Available Page File :"+ ( memSt.dwAvailPageFile/1024 ).ToString ( ) );
                   
                    listBox1.InsertItem( 11,"Available Physical Memory : " + ( memSt.dwAvailPhys/1024 ).ToString( ) );
                   
                    listBox1.InsertItem( 12,"Available Virtual Memory:" + ( memSt.dwAvailVirtual/1024 ).ToString ( ) );
                   
                    listBox1.InsertItem( 13,"Size of structur :" + memSt.dwLength.ToString( ) );
                   
                    listBox1.InsertItem( 14,"Memory In Use :"+ memSt.dwMemoryLoad.ToString( ) );
                   
                    listBox1.InsertItem( 15,"Total Page Size :"+ ( memSt.dwTotalPageFile/1024 ).ToString ( ) );
                   
                    listBox1.InsertItem( 16,"Total Physical Memory :" + ( memSt.dwTotalPhys/1024 ).ToString( ) );
                   
                    listBox1.InsertItem( 17,"Total Virtual Memory :" + ( memSt.dwTotalVirtual/1024 ).ToString ( ) );
                   
                }
               
                catch( Exception er )
               
                {
                   
                    MessageBox.Show ( er.Message );
                   
                }
               
            }
           
            public static void Main( string[] args )
           
            {
               
                try
               
                {
                   
                    Application.Run( new Form1( ) );
                   
                }
               
                catch( Exception er )
               
                {
                   
                    MessageBox.Show ( er.Message);
                   
                }
               
            }
           
        }
       
    }


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  • 原文地址:https://www.cnblogs.com/chorrysky/p/532973.html
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