Why Can't a Static Method Access Non-Static Members in C#?

C# static method cannot access the errors and solutions of non -static members

Error: The object is referenced

The following code fragment demonstrates this problem:

The cause of the problem

<code class="language-csharp">namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        ...

        private static void SumData(object state)
        {
            ...
            setTextboxText(result); // 错误：非静态字段、方法或属性
        }
    }
}</code>

Error information shows that static methods try to call non -static members

. Static methods can only access static members, and non -static members need a reference to objects that belong to.

SumData Solution setTextboxText

There are many ways to solve this error:

Set the

method as static:

1. setTextboxText However, if the method needs to access instance variables, it cannot be set to static.

Call

<code class="language-csharp">public static void setTextboxText(int result)</code>

:

setTextboxText

2. In the constructor, set to the current instance: Form1. setTextboxText
Create a

instance in the call method:

<code class="language-csharp">class Form1
{
    public static Form1 Instance;   // 单例

    ...

    private static void SumData(object state)
    {
        ...
        Instance.setTextboxText(result);
    }
}</code>

Form1 Instance Instance = this; If the instance already exists, this method may not be applicable.

3. The call method is set to non -static instance method (belongs to Form1):

<code class="language-csharp">private static void SumData(object state)
{
    ...
    Form1 frm1 = new Form1();
    frm1.setTextboxText(result);
}</code>

This is usually the best solution because it maintains the encapsulation and maintenance of the code. Form1

For more information, please refer to the MSDN document.

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