从数据库中填充Combobox

我有一个combobox的错误

我的代码：

SqlConnection conn = new SqlConnection(); try { conn = new SqlConnection(@"Data Source=SHARKAWY;Initial Catalog=Booking;Persist Security Info=True;User ID=sa;Password=123456"); string query = "select FleetName, FleetID from fleets"; SqlCommand cmd = new SqlCommand(query, conn); cmd.CommandText = query; conn.Open(); SqlDataReader drd = cmd.ExecuteReader(); while (drd.Read()) { cmbTripName.Items.Add(drd["FleetName"].ToString()); cmbTripName.ValueMember = drd["FleetID"].ToString(); cmbTripName.DisplayMember = drd["FleetName"].ToString(); } } catch { MessageBox.Show("Error "); } 

数据在combobox中显示，但是当您更改选择值时，显示成员不会更改。

它现在正在工作，但是当我点击按钮显示数据时

 private void button1_Click(object sender, EventArgs e) { label1.Text = cmbTripName.DisplayMember; label2.Text = cmbTripName.ValueMember; } 

显示如下：

FleetName
FleetID

它不显示值

Answer 1

您必须完全重写代码。 DisplayMember和ValueMember指向columnNames！ 此外，您应该使用using block – 因此在查询执行后连接将被释放 （和关闭 ）。

我没有使用dataReader来访问值，而是选择了dataTable并将其作为dataSource绑定到comboBox上。

 using (SqlConnection conn = new SqlConnection(@"Data Source=SHARKAWY;Initial Catalog=Booking;Persist Security Info=True;User ID=sa;Password=123456")) { try { string query = "select FleetName, FleetID from fleets"; SqlDataAdapter da = new SqlDataAdapter(query, conn); conn.Open(); DataSet ds = new DataSet(); da.Fill(ds, "Fleet"); cmbTripName.DisplayMember = "FleetName"; cmbTripName.ValueMember = "FleetID"; cmbTripName.DataSource = ds.Tables["Fleet"]; } catch (Exception ex) { // write exception info to log or anything else MessageBox.Show("Error occured!"); } } 

使用dataTable可能比dataReader 慢一点，但我不必创建自己的类 。 如果您真的必须/想要使用DataReader，您可以选择@Nattrass方法 。 无论如何你应该写一个使用块 ！

编辑

如果你想获得combobox的当前值，试试这个

 private void cmbTripName_SelectedIndexChanged(object sender, EventArgs e) { if (cmbTripName.SelectedItem != null) { DataRowView drv = cmbTripName.SelectedItem as DataRowView; Debug.WriteLine("Item: " + drv.Row["FleetName"].ToString()); Debug.WriteLine("Value: " + drv.Row["FleetID"].ToString()); Debug.WriteLine("Value: " + cmbTripName.SelectedValue.ToString()); } } 

Answer 2

要以您想要的方式使用Combobox ，您可以将对象传递给cmbTripName.Items.Add方法。

该对象应具有FleetID和FleetName属性：

 while (drd.Read()) { cmbTripName.Items.Add(new Fleet(drd["FleetID"].ToString(), drd["FleetName"].ToString())); } cmbTripName.ValueMember = "FleetId"; cmbTripName.DisplayMember = "FleetName"; 

Fleet类：

 class Fleet { public Fleet(string fleetId, string fleetName) { FleetId = fleetId; FleetName = fleetName } public string FleetId {get;set;} public string FleetName {get;set;} } 

或者，您可以通过使用匿名类型完全取消对Fleet类的需求……

 while (drd.Read()) { cmbTripName.Items.Add(new {FleetId = drd["FleetID"].ToString(), FleetName = drd["FleetName"].ToString()}); } cmbTripName.ValueMember = "FleetId"; cmbTripName.DisplayMember = "FleetName"; 

Answer 3

在循环外侧，设置如下。

 cmbTripName.ValueMember = "FleetID" cmbTripName.DisplayMember = "FleetName" 

Answer 4

  SqlConnection conn = new SqlConnection(@"Data Source=TOM-PC\sqlexpress;Initial Catalog=Northwind;User ID=sa;Password=xyz") ; conn.Open(); SqlCommand sc = new SqlCommand("select customerid,contactname from customers", conn); SqlDataReader reader; reader = sc.ExecuteReader(); DataTable dt = new DataTable(); dt.Columns.Add("customerid", typeof(string)); dt.Columns.Add("contactname", typeof(string)); dt.Load(reader); comboBox1.ValueMember = "customerid"; comboBox1.DisplayMember = "contactname"; comboBox1.DataSource = dt; conn.Close(); 

Answer 5

 private void StudentForm_Load(object sender, EventArgs e) { string q = @"SELECT [BatchID] FROM [Batch]"; //BatchID column name of Batch table SqlDataReader reader = DB.Query(q); while (reader.Read()) { cbsb.Items.Add(reader["BatchID"].ToString()); //cbsb is the combobox name } } 

Answer 6

 string query = "SELECT column_name FROM table_name"; //query the database SqlCommand queryStatus = new SqlCommand(query, myConnection); sqlDataReader reader = query.ExecuteReader(); while (reader.Read()) //loop reader and fill the combobox { ComboBox1.Items.Add(reader["column_name"].ToString()); } 

Answer 7

 void Fillcombobox() { con.Open(); cmd = new SqlCommand("select ID From Employees",con); Sdr = cmd.ExecuteReader(); while (Sdr.Read()) { for (int i = 0; i < Sdr.FieldCount; i++) { comboID.Items.Add( Sdr.GetString(i)); } } Sdr.Close(); con.Close(); }