WinForms C# ComboBox 設定值的幾種方式

範例說明下列情況:

如何在 combobox 賦予 items 預設值，如何從DB取值再加入combobox items 如何設定 combobox key value 值

public MYFORMS()
{
    InitializeComponent();
    MSSqlHelper.Initialize(); //初始化資料庫連線設定
    initCombobox();
}
private void initCombobox()
{
    //Order Buy Sell Kind
    cbdata = new Dictionary<string, string>();
    cbdata.Clear();
    cbdata.Add("1", "Yes");
    cbdata.Add("2", "No");
    DBELEM2.DataSource = new BindingSource(cbdata, null);
    DBELEM2.DisplayMember = "Value";
    DBELEM2.ValueMember = "Key";
    DBELEM2.SelectedIndex = -1;
}

private void MYFORMS_Load(object sender, EventArgs e)
{
    setCB();
}

private void setCB()
{
    dt = MSSqlHelper.GetDataTable("SELECT COMNAME FROM TABLENAME WHERE ID = 'A'", null);
    if (dt != null)
    {
        for (int i = 0; i < dt.Rows.Count; i++)
        {
            ComboboxItem item = new ComboboxItem();
            item.Text = "Name: "+dt.Rows[i]["COMNAME"].ToString();
            item.Value = dt.Rows[i]["COMNAME"].ToString();
            CBELEM.Items.Add(item);
        }
    }

}//.setCB

public class ComboboxItem
{
    public string Text { get; set; }
    public object Value { get; set; }

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

取得 COMBOBOX Key 值方式

如果使用 Text 只會取得 Value 屬性，可以透過 SelectedValue 取得 Key

若要在 ComboBox SelectedIndexChanged 的時候，判斷key執行動作時

記得要先在一開始寫入 if (COMBOBOX.SelectedValue == null){ return }

範例:

 if (COMBOBOX.SelectedValue == null)
{
    return;
}

string buy_sell_value = COMBOBOX.SelectedValue.ToString();

label11.Text = buy_sell_value;

switch (buy_sell_value)
{
    case "S":
        COMBOBOX.BackColor = Color.Red;
        break;
    case "B":
        COMBOBOX.BackColor = Color.Blue;
        break;
    default:
        COMBOBOX.BackColor = Color.White;
        break;
}