如何在c＃.net中从组合框中选择项目时触发事件 [英] how to trigger a event when an item is selected from combobox in c#.net

问题描述

  private   void  Form1_Load（ object  sender，EventArgs e）
 {
  string  Sql_type =   从lk_tb_property_type中选择property_type_id，type_name; 
 
 OleDbCommand cmd_type =  new  OleDbCommand（Sql_type，con）; 
 
 OleDbDataReader DR_two = cmd_type.ExecuteReader（）; 
 DataTable table_one =  new  DataTable（）; 
 table_one.Load（DR_two）; 
 
 DataRow row = table_two.NewRow（）; 
行[  type_name] =   选择Poperty Name; 
行[  property_type_id] =  0 ; 
 table_one.Rows.InsertAt（row， 0 ）; 
 
 comboBox1.DataSource = table_one; 
 comboBox1.DisplayMember =   name; 
 comboBox1.ValueMember =   id; 
 comboBox1.Text =  选择Poperty Name; 
} 

使用此代码我从database.now获取组合框的值。假设我的combobx有两个名为A和B的项目。我有一个更多的组合框...现在我想要的是当用户从组合框中选择项目A时，第二个组合框应该在用户选择项目B时显示与项目A相关的数据，那么应该显示与项目B相关的数据...所以如何实现这一点... ??

解决方案

检查这个



c＃c​​ombobox selectedindexchanged events [ ^ ]

你好，

我将只展示一个小例子这将显示使用comboboxselectedindexchanged事件，如上面的Karthik Sir所示：我将只展示一小段代码：

我有2个组合框：

combobox1和combobox2：



- 在combobox1中我填写了一个列表项目。



- 如果我从combobox1中选择一个项目，那么就像你想要的那样：

引用：

当用户从组合框中选择项目A时，当用户选择项目B时，第二个组合框应显示与项目A相关的数据，然后应显示与项目B相关的数据

以下是代码：

FORM CODE：

  public   partial   class  Form1：Form 
 {
  public  Form1（）
 {
 InitializeComponent（）; 
} 
 
  private   void  Form1_Load（ object  sender，EventArgs e）
 {
 
 load_first_ComboBox（）; 
} 
 
  public   void  load_first_ComboBox（）
 {
 List< string> list =  new 列表< string> {  a，  b，  c};  ///   //创建了一个列表，此列表将作为combobox1的源。在你的情况下，它将是数据库
  comboBox1.DataSource = list;  ///   /将combobox1绑定到源。 
 } 
 
  private   void  comboBox1_SelectedIndexChanged（< span class =code-keyword> object  sender，EventArgs e）
 {
  switch （comboBox1.SelectedItem.ToString（ ）） ///   //使用开关来测试从第一个组合框中选择的内容
  {
  case    a：
 comboBox2.Text =  您选择了;  ///   /与a相关的数据
  破; 
  case    b ：
 comboBox2.Text =  您选择了b;  ///   /与b相关的数据
  破; 
  case    c ：
 comboBox2.Text =  您选择了c;  ///   /与c相关的数据
  破; 
} 
} 
} 

- 我总是建议使用UI的人阅读有关背景工作者的文章。

- 如果处理增加，则UI变得无响应。要在背景工作者上克服这一点。



参考：

初学者的BackgroundWorker类示例 [ ^ ]



- 如果此代码有效，请告诉我，谢谢



非常感谢，

- Rahul

private void Form1_Load(object sender, EventArgs e)
{
    string Sql_type = "select property_type_id, type_name from lk_tb_property_type";

    OleDbCommand cmd_type = new OleDbCommand(Sql_type, con);

    OleDbDataReader DR_two = cmd_type.ExecuteReader();
    DataTable table_one = new DataTable();
    table_one.Load(DR_two);

    DataRow row = table_two.NewRow();
    row["type_name"] = "Select Poperty Name";
    row["property_type_id"] = 0;
    table_one.Rows.InsertAt(row, 0);

    comboBox1.DataSource = table_one;
    comboBox1.DisplayMember = "name";
    comboBox1.ValueMember = "id";
    comboBox1.Text = "Select Poperty Name";
}

with this code i am fetching values for a combobox from database.now suppose my combobx is having 2 items named A and B..I have one more combobox...now what i want is that when user chooses item A from combobox the second combobox should display data related to item A when user chooses item B then data related to item B should be displayed...so how to achieve this...??

解决方案

check this

c# combobox selectedindexchanged events[^]

Hello,
I will just demonstrate a small example which will show you the use of comboboxselectedindexchanged event as per illustrated by Karthik Sir above: i will just show a small piece of code:
I have 2 comboboxes:
combobox1 and combobox2:

- In combobox1 i have populated a list of items.

- If i select an item from combobox1, then as you wanted:

Quote:

when user chooses item A from combobox the second combobox should display data related to item A when user chooses item B then data related to item B should be displayed

Here is the code :
FORM CODE:

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

       private void Form1_Load(object sender, EventArgs e)
       {

           load_first_ComboBox();
       }

       public void load_first_ComboBox()
       {
           List<string> list = new List<string> { "a", "b", "c" }; /////created a list, this list will act as a source for the combobox1. In your case it will be the database
           comboBox1.DataSource = list;   ////bind the combobox1 to the source.
       }

       private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
       {
           switch (comboBox1.SelectedItem.ToString()) /////using switch to test as to what was selected from the first combobox
           {
               case "a":
                   comboBox2.Text = "you selected a"; ////data related to "a"
                   break;
               case "b":
                   comboBox2.Text = "you selected b"; ////data related to "b"
                   break;
               case "c":
                   comboBox2.Text = "you selected c"; ////data related to "c"
                   break;
           }
       }
   }

- I always suggest people who work with UI to read an article on backgroundworker.
- If the processing increases then UI becomes unresponsive.To overcome this read on backgroundworker.

Refer:
BackgroundWorker Class Sample for Beginners[^]

- Please let me know if this code works, thanks

Thanks a ton,
- Rahul

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