C# CS0120：非静态字段、方法或属性“foo”需要对象引用
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CS0120: An object reference is required for the nonstatic field, method, or property 'foo'
提问by huda
Consider:
考虑：
namespace WindowsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
//int[] val = { 0, 0};
int val;
if (textBox1.Text == "")
{
MessageBox.Show("Input any no");
}
else
{
val = Convert.ToInt32(textBox1.Text);
Thread ot1 = new Thread(new ParameterizedThreadStart(SumData));
ot1.Start(val);
}
}
private static void ReadData(object state)
{
System.Windows.Forms.Application.Run();
}
void setTextboxText(int result)
{
if (this.InvokeRequired)
{
this.Invoke(new IntDelegate(SetTextboxTextSafe), new object[] { result });
}
else
{
SetTextboxTextSafe(result);
}
}
void SetTextboxTextSafe(int result)
{
label1.Text = result.ToString();
}
private static void SumData(object state)
{
int result;
//int[] icount = (int[])state;
int icount = (int)state;
for (int i = icount; i > 0; i--)
{
result += i;
System.Threading.Thread.Sleep(1000);
}
setTextboxText(result);
}
delegate void IntDelegate(int result);
private void button2_Click(object sender, EventArgs e)
{
Application.Exit();
}
}
}
Why is this error occurring?
为什么会发生此错误？
An object reference is required for the nonstatic field, method, or property 'WindowsApplication1.Form1.setTextboxText(int)
非静态字段、方法或属性 'WindowsApplication1.Form1.setTextboxText(int) 需要对象引用
采纳答案by huda
It looks like you are calling a non static member (a property or method, specifically setTextboxText) from a static method (specifically SumData). You will need to either:
看起来您正在setTextboxText从静态方法（特别是SumData）调用非静态成员（特别是属性或方法）。您需要：
Make the called member static also:
static void setTextboxText(int result) { // Write static logic for setTextboxText. // This may require a static singleton instance of Form1. }Create an instance of
Form1within the calling method:private static void SumData(object state) { int result = 0; //int[] icount = (int[])state; int icount = (int)state; for (int i = icount; i > 0; i--) { result += i; System.Threading.Thread.Sleep(1000); } Form1 frm1 = new Form1(); frm1.setTextboxText(result); }Passing in an instance of
Form1would be an option also.Make the calling method a non-static instance method (of
Form1):private void SumData(object state) { int result = 0; //int[] icount = (int[])state; int icount = (int)state; for (int i = icount; i > 0; i--) { result += i; System.Threading.Thread.Sleep(1000); } setTextboxText(result); }
使被调用成员也静态：
static void setTextboxText(int result) { // Write static logic for setTextboxText. // This may require a static singleton instance of Form1. }Form1在调用方法中创建一个实例：private static void SumData(object state) { int result = 0; //int[] icount = (int[])state; int icount = (int)state; for (int i = icount; i > 0; i--) { result += i; System.Threading.Thread.Sleep(1000); } Form1 frm1 = new Form1(); frm1.setTextboxText(result); }传入一个实例也是
Form1一种选择。使调用方法成为非静态实例方法（of
Form1）：private void SumData(object state) { int result = 0; //int[] icount = (int[])state; int icount = (int)state; for (int i = icount; i > 0; i--) { result += i; System.Threading.Thread.Sleep(1000); } setTextboxText(result); }
More info about this error can be found on MSDN.
可以在 MSDN上找到有关此错误的更多信息。
回答by Brian Rasmussen
You start a thread which runs the static method SumData. However, SumDatacalls SetTextboxTextwhich isn't static. Thus you need an instance of your form to call SetTextboxText.
您启动一个运行静态方法的线程SumData。但是，SumData调用SetTextboxText不是静态的。因此，您需要一个表单实例来调用SetTextboxText.
回答by Abd Al-Kareem Attiya
From my looking you give a null value to a textbox and return in a ToString()as it is a static method. You can replace it with Convert.ToString()that can enable null value.
从我的角度来看，您为文本框提供了一个空值并在 a 中返回，ToString()因为它是一个静态方法。您可以将其替换为 Convert.ToString()可以启用空值。
回答by issam chouchane
Your method must be static
你的方法必须是静态的
static void setTextboxText(int result)
{
if (this.InvokeRequired)
{
this.Invoke(new IntDelegate(SetTextboxTextSafe), new object[] { result });
}
else
{
SetTextboxTextSafe(result);
}
}
回答by COOLGAMETUBE
For this case, where you want to get a Control of a Form and are receiving this error, then I have a little bypass for you.
对于这种情况，您想要获得表单控件并收到此错误，那么我为您提供了一些绕过。
Go to your Program.cs and change
转到您的 Program.cs 并更改
Application.Run(new Form1());
to
到
public static Form1 form1 = new Form1(); // Place this var out of the constructor
Application.Run(form1);
Now you can access a control with
现在你可以访问一个控件
Program.form1.<Your control>
Also: Don't forget to set your Control-Access-Level to Public.
另外：不要忘记将您的控制访问级别设置为公共。
And yes I know, this answer does not fit to the question caller, but it fits to googlers who have this specific issue with controls.
是的，我知道，这个答案不适合提问者，但适合有这个特定控件问题的谷歌员工。
回答by veggiebenz
Credit to @COOLGAMETUBE for tipping me off to what ended up working for me. His idea was good but I had a problem when Application.SetCompatibleTextRenderingDefault was called after the form was already created. So with a little change, this is working for me:
感谢@COOLGAMETUBE 向我透露了最终对我有用的东西。他的想法很好，但我在创建表单后调用 Application.SetCompatibleTextRenderingDefault 时遇到了问题。所以稍作改动，这对我有用：
static class Program
{
public static Form1 form1; // = new Form1(); // Place this var out of the constructor
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(form1 = new Form1());
}
}
回答by Max Alexander Hanna
I actually got this error because I was checking InnerHtml for some content that was generated dynamically - i.e. a control that is runat=server.
我实际上收到了这个错误，因为我正在检查 InnerHtml 中是否有一些动态生成的内容 - 即 runat=server 的控件。
To solve this I had to remove the "static" keyword on my method, and it ran fine.
为了解决这个问题，我必须在我的方法中删除“static”关键字，并且它运行良好。
