填充组合框并在文本框中显示有错误 [英] Populating combobox and displayin in the text box has error

问题描述

填充combox并在组合框中显示值
例如如果我在组合框中选择名称，则相应的ID应显示在文本框中.有人知道吗?我正在学习C#.我尝试过可以让任何人检查以下代码.

阅读后，我尝试将其放入绑定列表数组中，然后我说
combobox1.datasorce =新变量

Pl.检查以下代码.

populating the combox and displaying the value in the combobox
for eg. if I choose name in the combobox the corresponding ID should display in the text box . Do anybody know? I am learning c#. I tried it can anybody examine the following code.

After reading I tried to put it in a Binding list array and then I said
combobox1.datasorce = the new variable

Pl. examine the below code.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;
namespace DBExample
{
    public partial class Form1 : Form
    {
        private OleDbConnection dbConn; // Connectionn object
        private OleDbCommand dbCmd;     // Command object
        private OleDbDataReader dbReader;// Data Reader object
        private Member aMember;
        private string sConnection;
        // private TextBox tb1;
        // private TextBox tb2;
        private string sql;
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                // Construct an object of the OleDbConnection 
                // class to store the connection string 
                // representing the type of data provider 
                // (database) and the source (actual db)
                sConnection =
                    "Provider=Microsoft.Jet.OLEDB.4.0;" +
                    "Data Source=c:member.mdb";
                dbConn = new OleDbConnection(sConnection);
                dbConn.Open();
                // Construct an object of the OleDbCommand 
                // class to hold the SQL query. Tie the  
                // OleDbCommand object to the OleDbConnection
                // object
                sql = "Select * From memberTable Order " +
                      "By LastName , FirstName ";
                dbCmd = new OleDbCommand();
                dbCmd.CommandText = sql;
                dbCmd.Connection = dbConn;
                // Create a dbReader object 
                dbReader = dbCmd.ExecuteReader();
                while (dbReader.Read())
                {
                    aMember = new Member
                            (dbReader["FirstName"].ToString(),
                             dbReader["LastName"].ToString(),
                             dbReader["StudentId"].ToString(),
                             dbReader["PhoneNumber"].ToString());
                    // tb1.Text = dbReader["FirstName"].ToString();
                    // tb2.Text = dbReader["LastName"].ToString();
                    // tb1.Text = aMember.X().ToString();

                    //tb2.Text = aMember.Y(aMember.ID).ToString();  
                    BindingList<Member> comboBoxList = new BindingList<Member>();
                    
                    comboBox1.DataSource = comboBoxList; 
                    comboBox1.DisplayMember = "FirstName"; 
                    comboBox1.ValueMember = "ID";
                   // this.comboBox1.Items.Add("aMember.FirstName.ToString()");
                    // this.listBox1.Items.Add(aMember.ToString());
                    // MessageBox.Show(aMember.ToString());
                    // Console.WriteLine(aMember.ToString());
                }
                dbReader.Close();
                dbConn.Close();
            }
            catch (System.Exception exc)
            {
                MessageBox.Show("show" + exc);
            }
        }
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
         // textBox2.DataBindings.Add("Text", aMember, "aMember.ID");
            textBox2.Text = comboBox1.SelectedValue.ToString();
            this.textBox1.Text = comboBox1.SelectedItem.ToString();
            //int[] item = (int[])comboBox1.SelectedItem;
            //textBox2.Text = string.Empty;
           // foreach (int i in item)
           //    textBox2.Text += item.ToString();
            
}
         
  
        private void DbGUI_Load(object sender, EventArgs e)
        {
        }

        

        private void textBox2_TextChanged(object sender, EventArgs e)
        {
           
        }
        private void textBox1_TextChanged(object sender, EventArgs e)
        {
        }
    }



}

推荐答案

您应该像这样修改代码，

You should modify your code like this,

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
         if (comboBox1.SelectedIndex > 0)
          {

         // textBox2.DataBindings.Add("Text", aMember,     "aMember.ID");
            textBox2.Text = comboBox1.SelectedValue.ToString();
            this.textBox1.Text = comboBox1.SelectedItem.ToString();
            //int[] item = (int[])comboBox1.SelectedItem;
            //textBox2.Text = string.Empty;
           // foreach (int i in item)
           //    textBox2.Text += item.ToString();
          }
}

最好的问候，
Theingi Win

Best Regards,
Theingi Win

嗨

在while循环之前将其移动

BindingList<member> comboBoxList = new BindingList<member>();</member></member>

绑定列表是一个信号实例，无需在循环中一次又一次地实例化

在while循环中获取此

Hi

Move this before the while loop

BindingList<member> comboBoxList = new BindingList<member>();</member></member>

Binding list is a signle instance, no need to instantiate again and again inside the loop

inside the while loop get this

Member mem1 = new Member("Student A", "Student A", 1, "XXXXXXX");
Member mem2 = new Member("Student B", "Student B", 2, "XXXXXXX");

comboBoxList.Add(mem1);
comboBoxList.Add(mem2);

您必须使用成员填充绑定列表

然后在while循环之外将其分配给组合框

You have to populate the binding list with members

Then out side the while loop assign this to the combobox

comboBox1.DataSource = comboBoxList;
comboBox1.DisplayMember = "FirstName";
comboBox1.ValueMember = "ID";

然后在Selection Change Event

Then in the Selection Change Event

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    Member mem=(Member)comboBox1.SelectedItem;
    textBox1.Text = mem.FirstName;
}

您正在做的是创建绑定列表，但是该绑定列表为空.

What you are doing is creating a binding list, but that binding list is empty.

您好
请尝试以下代码块

Hi
Please try the below code block

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
         // textBox2.DataBindings.Add("Text", aMember, "aMember.ID");
            textBox2.Text = comboBox1.SelectedValue.ToString();
            this.textBox1.Text = comboBox1.Text;
            //int[] item = (int[])comboBox1.SelectedItem;
            //textBox2.Text = string.Empty;
           // foreach (int i in item)
           //    textBox2.Text += item.ToString();
}

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