C#中的错误:“非静态字段,方法或属性需要对象引用” [英] Error in C#: "An object reference is required for the non-static field, method, or property"
问题描述
我用WPF编写了代码。首先,我编写了一个单独的项目来测试 COM端口设备的工作,然后它运作良好。接下来,我决定将其集成到另一个项目中,但出现错误。我没有更改代码;我只是将其复制到新的代码文件中。
I wrote code in WPF. Firstly, I wrote a separate project to test work with a COM port device, and it worked well. Next I decided to integrate it in another project, but I get an error. I didn't change the code; I am just copied it into a new code file.
此代码效果很好:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.IO.Ports;
using System.Windows.Threading;
namespace WpfApplication2
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
serial.BaudRate = 9600;
serial.Handshake = System.IO.Ports.Handshake.None;
serial.Parity = Parity.None;
serial.DataBits = 8;
serial.StopBits = StopBits.One;
serial.ReadTimeout = 200;
serial.WriteTimeout = 500;
serial.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(Recieve);
}
SerialPort serial = new SerialPort();
private string recieved_data;
private delegate void UpdateUiTextDelegate(string text);
private void Recieve(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
if (serial.IsOpen)
{
try
{
recieved_data = serial.ReadLine();
Dispatcher.Invoke(DispatcherPriority.Send, new UpdateUiTextDelegate(DisplayText), recieved_data);
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
}
private void DisplayText(string code)
{
textBox1.AppendText(string1);
}
private void button1_Click(object sender, RoutedEventArgs e)
{
ListBoxItem lbi = new ListBoxItem();
lbi = (ListBoxItem)listBox1.SelectedItem;
serial.Close();
serial.PortName = "COM" + (string)lbi.Content;
try
{
serial.Open();
textBox1.AppendText("Device opened at " + serial.PortName + '\n');
}
catch (Exception ex)
{
textBox1.AppendText(ex.Message + '\n');
}
}
}
}
但是那个不想工作,我也不明白为什么:
But this one doesn't want to work, and I can't understand why:
using System.IO.Ports;
using System.Windows.Threading;
using System;
using System.Windows;
namespace PresidentProtocol
{
public class QRBarCode
{
// private SerialPort serial = new SerialPort();
public QRBarCode(string com)
{
serial.BaudRate = 9600;
serial.Handshake = System.IO.Ports.Handshake.None;
serial.Parity = Parity.None;
serial.DataBits = 8;
serial.StopBits = StopBits.One;
serial.ReadTimeout = 200;
serial.WriteTimeout = 500;
serial.DataReceived += new System.IO.Ports.SerialDataReceivedEventHandler(Recieve);
serial.Close();
serial.PortName = com;
try
{
serial.Open();
}
catch (Exception)
{
MessageBox.Show("Error opening COM port.");
}
}
SerialPort serial = new SerialPort();
private string recieved_data;
private delegate void UpdateUiTextDelegate(string text);
private void Recieve(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
if (serial.IsOpen)
{
try
{
recieved_data = serial.ReadLine();
Dispatcher.Invoke(DispatcherPriority.Send, new UpdateUiTextDelegate(DisplayText), recieved_data);
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
}
}
private void DisplayText(string code)
{
MessageBox.Show(code);
}
}
}
错误:
非静态字段,方法或属性'System.Windows.Threading.Dispatcher.Invoke(System.Windows.Threading .DispatcherPriority,System.Delegate,object)'
E:\C#\PresidentProtocol\PresidentProtocol\classes\QRCodeReader.cs
An object reference is required for the non-static field, method, or property 'System.Windows.Threading.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority, System.Delegate, object)' E:\C#\PresidentProtocol\PresidentProtocol\classes\QRCodeReader.cs
在以下代码行上:
Dispatcher.Invoke(DispatcherPriority.Send, new UpdateUiTextDelegate(DisplayText), recieved_data);
推荐答案
在第一个代码中,您所在的类是从 Window
继承,因此您在范围内有一个 Dispatcher
属性,该属性返回的实例调度程序
。在第二个代码中,您位于 QRBarCode
类中,该类没有 Dispatcher
属性;因此编译器假定您引用的是 Dispatcher
类型,并尝试对此类型调用 Invoke
,但是由于它不是静态方法,不能直接在类型上调用。
In the first code, you are in a class that inherits from Window
, so you have a Dispatcher
property in scope, which returns an instance of Dispatcher
. In the second code, you're in the QRBarCode
class, which doesn't have a Dispatcher
property; so the compiler assumes you're referring to the Dispatcher
type, and tries to call Invoke
on this type, but since it's not a static method, it can't be called directly on the type.
您需要一个 Dispatcher
调用调用
;您可以使用应用程序中的一个:
You need an instance of Dispatcher
to call Invoke
; you can use the one from the application:
Application.Current.Dispatcher.Invoke(...);
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