为什么我会收到 NullException？
我搜索了一段时间，没有找到解决方案，还是我只是没有看到这个小错误？
我用 Visual C# 编写了一个程序 Form1.cs 程序.cs Server.cs
Server.cs
namespace WindowsApplication1 {
class testServer {
public Form1 form1;
form1.send("data");
Program.cs
using System;
using System.Collections.Generic;
using System.Windows.Forms;
namespace WindowsApplication1
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
}
Form1.cs
namespace WindowsApplication1
{
public partial class Form1 : System.Windows.Forms.Form
{
public Form1()
{
InitializeComponent();
}
private testServer Server;
private void startServer_Click(object sender, System.EventArgs e)
{
Server = new Server(data);
Server.form1 = this;
}
一切正常，但在 Server.cs 中我得到一个 nullException form1.send("data"); 看来 form1 确实为空，但为什么呢？
我哪里忘记了什么？
I searched a while and found no solution or do I just not see the little error?
I wrote a program with Visual C# and have
Form1.cs
Program.cs
Server.cs
Server.cs
namespace WindowsApplication1 {
class testServer {
public Form1 form1;
form1.send("data");
Program.cs
using System;
using System.Collections.Generic;
using System.Windows.Forms;
namespace WindowsApplication1
{
static class Program
{
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
}
Form1.cs
namespace WindowsApplication1
{
public partial class Form1 : System.Windows.Forms.Form
{
public Form1()
{
InitializeComponent();
}
private testServer Server;
private void startServer_Click(object sender, System.EventArgs e)
{
Server = new Server(data);
Server.form1 = this;
}
Everything works but in Server.cs I get a nullexception with form1.send("data");
It seems form1 is really null but why?
Where did I forget something?
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评论（5）
您必须创建 Form1 的实例，尝试
You have to create an instance of Form1, try
form1 永远不会被实例化。这是您的 NullReferenceException (NRE)。
更好的：
form1 is never instantiated. There is your NullReferenceException (NRE).
Better:
也许您忘记将
testServer中的form1变量分配给构造参数。顺便说一句：您的代码看起来不像好的设计：您不应该传递 Form 对象。
Maybe you forgot to assign the
form1variable intestServerto the construct parameter.BTW: You code doesn't look like good design: You shouldn't pass Form objects around.
它是空的，因为你没有初始化它。
It is null because you're not initializing it.
form1变量在代码中使用之前未初始化The
form1variable is not initialised before being used in the code