我的组合框出现错误
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 ");
}
数据显示在组合框中,但是当您 更改选择值成员时,显示成员不会更改。
它现在正在工作,但是当我单击按钮显示数据时
private void button1_Click(object sender, EventArgs e)
{
label1.Text = cmbTripName.DisplayMember;
label2.Text = cmbTripName.ValueMember;
}
显示:
舰队名称
舰队ID
不显示数值
您将必须完全重写您的代码。 DisplayMember和ValueMember指向columnNames!此外,您确实应该使用
using block
- 因此连接在查询执行后会被 dispose (和 lined)。
我没有使用 dataReader 来访问值,而是选择了 dataTable 并将其作为数据源绑定到组合框上。
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。如果您确实必须/想要使用DataReader,您可以选择@Nattrass方法。无论如何,你应该写一个 using 块!
编辑
如果您想获取组合框的当前值,请尝试此
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());
}
}
Combobox
,您可以将一个对象传递给
cmbTripName.Items.Add
方法。该对象应该具有
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
班级:
class Fleet
{
public Fleet(string fleetId, string fleetName)
{
FleetId = fleetId;
FleetName = fleetName
}
public string FleetId {get;set;}
public string FleetName {get;set;}
}
或者,您可能可以通过使用匿名类型完全消除对
Fleet
类的需要...
while (drd.Read())
{
cmbTripName.Items.Add(new {FleetId = drd["FleetID"].ToString(), FleetName = drd["FleetName"].ToString()});
}
cmbTripName.ValueMember = "FleetId";
cmbTripName.DisplayMember = "FleetName";
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();
}
cmbTripName.ValueMember = "FleetID"
cmbTripName.DisplayMember = "FleetName"
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();
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
}
}
string query = "SELECT column_name FROM table_name"; //query the database
SqlCommand queryStatus = new SqlCommand(query, myConnection);
sqlDataReader reader = queryStatus.ExecuteReader();
while (reader.Read()) //loop reader and fill the combobox
{
ComboBox1.Items.Add(reader["column_name"].ToString());
}
using MySql.Data.MySqlClient;
MySqlConnection con = new MySqlConnection("datasource=172.16.2.104;port=3306;server=localhost;database=DB_Name;uid=root;password=DB_Password;sslmode=none;charset=utf8;");
MySqlCommand cmd = new MySqlCommand();
var query2 = "SELECT `salary` FROM `employees_db` ";
using (var command2 = new MySqlCommand(query2, con))
{
using (var reader2 = command2.ExecuteReader())
{
while (reader2.Read())
{
combox.Text = reader2.GetString("salary");
}
}
}
private void button1_Click(object sender, EventArgs e)
{
label1.Text = cmbTripName.Text;
label2.Text = cmbTripName.SelectedValue.ToString();
}