无法打开并保存文件MDI表单？请帮忙 [英] Unable to open and save file MDI forms ? please help

问题描述

我创建了一个Windows MDI表单，其中我有menustrip



Form1 - 是mdi容器



表格2（新文件） - 包含richtextbox1



如何以父表格（Form1）访问Form2 richtextbox



当我在saveFileDialog窗口中点击保存时抛出我的错误



对象实例未设置为对象的实例



我尝试过：



private void openToolStripMenuItem_Click（object sender，EventArgs e）

$



DialogResult博士;

dr = openFileDialog1.ShowDialog（）;

if（dr == DialogResult.OK）

{



rtbb.LoadFile（openFileDialog1.FileName）;

this。 Text = openFileDialog1.FileName;



}

I have created a windows MDI form in which i have menustrip

Form1 - is mdi container

Form 2 (New file) - contains richtextbox1

How can i access Form2 richtextbox in parent Form(Form1)

when i click save in saveFileDialog window throws me error

Object instance not set to an instance of an object

What I have tried:

private void openToolStripMenuItem_Click(object sender, EventArgs e)
{

DialogResult dr;
dr = openFileDialog1.ShowDialog();
if (dr == DialogResult.OK)
{

rtbb.LoadFile(openFileDialog1.FileName);
this.Text = openFileDialog1.FileName;

}

推荐答案

您没有显示带有对象引用未设置为对象实例消息的异常位置。



不是担心。这是检测和修复的最简单的案例之一。它只是意味着某些引用类型的某个成员/变量通过使用及其实例（非静态）成员进行解引用，这需要此成员/变量为非null，但实际上它似乎为null。只需在调试器下执行它，它将停止抛出异常的执行。在该行上设置一个断点，重新启动应用程序并再次到达这一点。评估下一行中涉及的所有引用，并查看哪一个为null，而不需要为null。解决这个问题之后，修复代码：要么确保将成员/变量正确初始化为非空引用，要么将其检查为null，如果为null，则执行其他操作。



另请参阅：想要在按钮点击时显示下一条记录。但是如果下一个记录功能的条件对象引用未设置为对象的实例则会出错。



有时候，你不能这样做在调试器下，由一个或另一个原因。一个非常讨厌的情况是，只有在调试信息不​​可用时构建软件时才会出现问题。在这种情况下，你必须使用更难的方式。首先，你需要确保你永远不会通过静默处理异常来阻止异常的传播（这是开发人员对自己的犯罪，但很常见）。您需要在每个线程的最顶层堆栈帧上捕获绝对所有异常。如果处理类型 System.Exception 的异常，则可以执行此操作。在处理程序中，您需要记录所有异常信息，尤其是 System.Exception.StackTrace ：

http://msdn.microsoft.com/en-us/library/system.exception.aspx ，

http://msdn.microsoft.com/en-us/library/ system.exception.stacktrace.aspx 。



堆栈跟踪只是一个字符串，显示从throw语句到处理程序的异常传播的完整路径。通过阅读，您总能找到目的。对于日志记录，使用类 System.Diagnostics.EventLog ：

http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx 。



现在，我想就MDI给你一些建议。以下是这个想法：谁需要MDI？为什么要折磨自己并吓跑你的用户？

帮自己一个大忙：根本不要使用MDI。没有它，您可以更轻松地实现设计，质量更好。 MDI甚至被微软高度劝阻，事实上，微软将其从WPF中删除并且很难支持它。更重要的是，如果您使用MDI，您将吓跑所有用户。只是不要。请参阅：

http://en.wikipedia.org/wiki/Multiple_document_interface#Disadvantages，

如何在WPF中创建MDI父窗口？。



我可以解释做什么。请看我过去的答案：

如何在WPF中创建MDI父窗口？，

关于在WPF中使用MDI窗口的问题，

MDIContainer给出错误，

如何设置最大化的子表单，最小化最后一个子表单。



祝你好运，

-SA

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown.

Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferences by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object".

Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the type System.Exception. In the handler, you need to log all the exception information, especially the System.Exception.StackTrace:
http://msdn.microsoft.com/en-us/library/system.exception.aspx,
http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx.

The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the class System.Diagnostics.EventLog:
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx.

Now, I would like to give you a little advice on MDI. Here is the idea: who needs MDI, ever? Why torturing yourself and scaring off your users?
Do yourself a great favor: do not use MDI at all. You can do much easier to implement design without it, with much better quality. MDI is highly discouraged even by Microsoft, in fact, Microsoft dropped it out of WPF and will hardly support it. More importantly, you will scare off all your users if you use MDI. Just don't. Please see:
http://en.wikipedia.org/wiki/Multiple_document_interface#Disadvantages,
How to Create MDI Parent Window in WPF?.

I can explain what to do instead. Please see my past answers:
How to Create MDI Parent Window in WPF?,
Question on using MDI windows in WPF,
MDIContainer giving error,
How to set child forms maximized, last childform minimized.

Good luck,

—SA

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