c#如何在c#中显示组合框中的名称和插入值(名称ID)

Question

提前谢谢你们.我是c#Windows Forms中的新用户.

我有一张带有id和名字的表

ID  | Name
---------------
1   | Lion
2   | Tiger
3   | Crocodile

如果我想从表格显示到组合框,我确实喜欢这样.

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.SqlClient;

namespace Insert_update_delete_nr2
{
    public partial class Form1 : Form
    {
        SqlConnection con = new SqlConnection(@"CONNECTION_STRING");

        SqlCommand cmd = new SqlCommand();
        SqlDataReader dr;
        public Form1()
        {
            InitializeComponent();
        }


        private void button1_Click_1(object sender, EventArgs e)
        {

                con.Open();

                string query = "select * from info";
                SqlCommand cmd = new SqlCommand(query, con);
                cmd.CommandType = CommandType.Text;
                dr = cmd.ExecuteReader();


                while (dr.Read())//while true
                {

                    comboBox1.Items.Add(dr[0].ToString());//loading values into combo
                }

                cmd.CommandText = "insert into info3 (name, name_id) values ('"+textBox1.Text+"', '" + comboBox1.Items.Add(dr[0].ToString()) + "')";
                cmd.ExecuteNonQuery();

                cmd.Clone();
                con.Close();

        }

        private void loadlist()
        {
            listBox1.Items.Clear();
            listBox2.Items.Clear();
            listBox3.Items.Clear();
            con.Open();

            cmd.CommandText = "select * from info3";
             dr = cmd.ExecuteReader();
            if (dr.HasRows)
            {
                while (dr.Read())
                {
                    listBox1.Items.Add(dr[0].ToString());
                    listBox2.Items.Add(dr[1]).ToString();
                    listBox3.Items.Add(dr[3].ToString());


                }
            }
            con.Close();


        }

        private void Form1_Load(object sender, EventArgs e)
    {

       // con.Open();
        FillDropDownList(string SQL, ComboBox comboBox1);// This giving me error.
        // How should I call this FillDropDownlist function? The parameters which are they?
        cmd.Connection = con;
        listBox3.Visible = false;

        loadlist();

    }



    }
}

它正在尝试插入组合框中显示的名称,而不是id的.

在PHP中它将如下所示:

$sql =  " SELECT * FROM info ";
$res = mysql_query($sql);
while ($row = mysql_fetch_array($res)) {
    print '<option value="'.$row['id'].'">'.$row['name'].'</option>';
}

那将插入id并显示名称.但是我应该怎么做c#？再次感谢您的时间!

Answer 1

您可以添加自定义类型,而不是将名称字符串添加到组合框中:

class Animal
{
    public int ID { get; set; }
    public string Name { get; set; }

    public override string ToString()
    {
        return Name;
    }
}

为每个条目(var animal = new Animal { ID = (int)dr[0], Name = (string)dr[1] };)创建该类型的对象,将对象添加到组合框.然后,当您去检索它时,只需将项目转换为Animal类型并获取ID.

var animal = (Animal)comboBox1.SelectedItem;

Answer 2

如果我正确理解你的问题，这应该可以满足你的要求：

用这样的东西加载你的组合框（我现在无法测试这个，所以我可能犯了一些拼写错误或轻微的语法错误）：

* *更新：好的。这是我最后一次在匆忙中尝试“在旅途中”回答问题。我原来的代码充满了问题和愚蠢的拼写错误。谨致诚挚的歉意！以下代码包含您尝试执行的所有操作的非常基本的版本。您可能需要对其进行调整以满足您的需求。

一些建议：

A. 将连接和命令放置在 using 块中，如图所示。

B. 不要在代码中对连接字符串进行硬编码，而是使用解决方案资源管理器（位于左侧）中的 Properties.Settings 设计器，并为连接字符串创建中央引用。然后在代码中引用它，如图所示。

以下代码执行您想要实现的基本功能，并在我的机器上运行：

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


    private void Form1_Load(object sender, EventArgs e)
    {
        button1.Click += new EventHandler(button1_Click);
        this.FillDropDownList();
    }


    void button1_Click(object sender, EventArgs e)
    {
        this.SaveComboBoxContent();
    }


    public void FillDropDownList()
    {
        string SQL = "SELECT id, name FROM info ORDER BY name";

        DataTable dt = new DataTable();

        // Set the connection string in the Solutions Explorer/Properties/Settings object (double-click)
        using (var cn = new SqlConnection(Properties.Settings.Default.MyConnectionString))
        {
            using(var cmd = new SqlCommand(SQL, cn))
            {
                cn.Open();

                try
                {
                    dt.Load(cmd.ExecuteReader());
                }
                catch (SqlException e)
                {
                    // Do some logging or something. 
                    MessageBox.Show("There was an error accessing your data. DETAIL: " + e.ToString());
                }
            }
        }

        // UPDATED - The .ValueMember and .DisplayMember properties 
        // refer to the string name of the field (oops!):
        comboBox1.DataSource = dt;
        comboBox1.ValueMember = "id";
        comboBox1.DisplayMember = "name";
    }


    public void SaveComboBoxContent()
    {
        string SQL = "INSERT INTO info2 (name_id) VALUES (@name_id)";

        using (var cn = new SqlConnection(Properties.Settings.Default.MyConnectionString))
        {
            using(var cmd = new SqlCommand(SQL, cn))
            {
                cmd.Parameters.AddWithValue("@name_id", comboBox1.SelectedValue);
                cn.Open();

                try
                {
                    cmd.ExecuteNonQuery();
                }
                catch (SqlException e)
                {
                    // Do some logging or something. 
                    MessageBox.Show("There was an error accessing your data. DETAIL: " + e.ToString());
                }
            }
        }
    }

}

希望有帮助。