如何在C#表单中修改标签文本 [英] How to modify label text in C# forms

问题描述

(我对C#还是很陌生)正在创建一个表单应用程序，目的是从Web API获取字符串，然后将该文本放在标签上.我已经成功地从Web上获取了数据，但是当我尝试更新标签时，我没有运气. 我已经调试，发现我的类 Is 中的方法正在执行，但没有设置标签的文本.如下所示，我尝试使用this.resultLabel.text = str;.这是课程:

(I am very new to C#) I am creating a forms application, and the purpose is to get a string from a Web API, then put that text onto a label. I have successfully gotten the data from the Web, but when I try to update the label, I have no luck. I have debugged and found that my method inside my class Is executing, but just not setting the label's text. As you can see below, I tried to use this.resultLabel.text = str;. Here's the classes:

Program.cs(不是CS文件格式)

Program.cs (not the form cs file)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Net.Http;
using System.Net;
using System.IO;
namespace WebsiteAPITest
{
    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());

        }

    }
    class PostManager
    {
        public void setupClient()
        {


            HttpWebRequest WebReq = (HttpWebRequest)WebRequest.Create(string.Format("https://yakovliam.com/phpApi/csTest.php"));

            WebReq.Method = "GET";

            HttpWebResponse WebResp = (HttpWebResponse)WebReq.GetResponse();

            string respStr;
            using (Stream stream = WebResp.GetResponseStream())   //modified from your code since the using statement disposes the stream automatically when done
            {
                StreamReader reader = new StreamReader(stream, System.Text.Encoding.UTF8);
                respStr = reader.ReadToEnd();
            }

            MessageBox.Show(respStr);
            Form1 form = new Form1();
            form.SetResultLabel(respStr);

        }


    }

}

实际表单类(Form1.cs)

Actual form class (Form1.cs)

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WebsiteAPITest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void GetButton_Click(object sender, EventArgs e)
        {
            PostManager postManager = new PostManager();
            postManager.setupClient();
        }
        public void SetResultLabel(string str)
        {
            this.resultLabel.Text = str;
            this.resultLabel.Refresh();
        }
    }

标签名称证明:

推荐答案

在setupClient内部，您调用Form1 form = new Form1()；会创建另一个您永远不会显示的Form1，然后在您从未显示的第二个表单中调用SetResultLabel(respStr)，然后离开该方法并将其丢弃.

Inside setupClient you call Form1 form = new Form1(); that creates a second Form1 which you never display, then you call SetResultLabel(respStr) inside this second form you never display, then you leave the method and discard it.

如果要致电呼叫表格的SetResultLabel，则必须将呼叫表格传递给setupClient:

If you want to call SetResultLabel of your calling form, you have to pass the calling form to setupClient:

public void setupClient(Form1 callingForm)
{
    ...
    callingForm.SetResultLabel(respStr);

然后在您的Form1内:

postManager.setupClient(this);

将表格传递给其他方法非常危险；更好的设计是让其他方法将数据返回到表单:

It's quite dangerous to pass forms to other methods; a better design is to have the other method return data to your form:

public string setupClient()
{
    ...
    return respStr;
}

在Form1内部:

SetResultLabel(postManager.setupClient());

这篇关于如何在C#表单中修改标签文本的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！