Question

我有一个由DataTable填充的组合框，如下所示。我希望能够设置显示的项目。它要设置的值是一个字符串，可以在“Id”列中找到。

public DataTable list = new DataTable();
public ComboBox cbRates = new ComboBox();

//prepare rates combo data source
this.list.Columns.Add(new DataColumn("Display", typeof(string)));
this.list.Columns.Add(new DataColumn("Id", typeof(string)));

//populate the rates combo
int counter = 0;

foreach (string item in dropdownItems)
{
    this.list.Rows.Add(list.NewRow());
    if (counter == 0)
    {
    this.list.Rows[counter][0] = "Select Rate..";
    this.list.Rows[counter][1] = "";
}
else
{
string[] itemSplit = item.Split('`');
if (itemSplit.Length == 2)
{
    this.list.Rows[counter]["Display"] = itemSplit[0];
    this.list.Rows[counter]["Id"] = itemSplit[1];
}
else
{
    this.list.Rows[counter]["Display"] = item;
    this.list.Rows[counter]["Id"] = item;
}
}
counter++;
}
this.cbRates.DataSource = list;
this.cbRates.DisplayMember = "Display";
this.cbRates.ValueMember = "Id";

//now.. how to set the selected value?

int rowCount = 0;
foreach (DataRow cbrow in this.list.Rows)
{
    if (DB.GetString(cbrow["Id"]) == answerSplit[1])
    {
        //attempting to set the SelectedIndex throws an exception
        //on another combobox populated NOT from a DataTable - this does work fine.
        this.cbRates.SelectedIndex = rowCount;
    }
    rowCount++;
}

//this doesn't seem to do anything.
foreach (DataRow dr in this.list.Rows)
{
    if ((string)dr["Id"] == answerSplit[1]) this.cbRates.SelectedItem = dr;
}

//nor this
foreach(DataRow dr in this.cbRates.Items)
{
   try
   {
     if ((string)dr["Id"] == answerSplit[1]) this.cbRates.SelectedItem = dr;
   }
    catch
    {
      MessageBox.Show("Ooops");
    }
}

如果没有FindExactString，FindString，FindByValue在紧凑的框架中不存在，我将无法尝试。

如果尝试使用

this.cbRates.SelectedIndex = 2;

我收到以下错误;

System.Exception: Exception
at Microsoft.AGL.Common.MISC.HandleAr(PAL_ERROR ar)
at System.Windows.Forms.ComboBox.set_SelectedIndex(Int32 value)

但是，如果我将相关代码放入其自己的表单中以进行测试，我可以设置selectedIndex而不会出错。

我认为这些问题是相互关联的。

Answer 1

您是否知道可以直接将数据表用作数据源？

        cbo.DataSource = table;
        cbo.DisplayMember = "Display";
        cbo.ValueMember = "Id";

Answer 2

您是否尝试设置SelectedValue？您有一个Id，并且您声明ValueMember是Id，然后使用它。

Answer 3

你可以做到这一点，如果你有大量的物品，它可以工作但不会太快：

foreach (object item in comboBox1.Items)
{
    DataRowView row = item as DataRowView;
    if ((String)row["YourDisplayMemberColumn"] == "ValueYouWantToSelect")
    {
        comboBox1.SelectedItem = item;
    }
}

Answer 4

您可以通过找到与指定字符串ComboBox.FindStringExact方法完全匹配的项目来设置SelectedIndex

cbRates.SelectedIndex = cbRates.FindStringExact("Value_need_to_Select") ;

选择从DataTable填充的组合框中的值

4 个答案: