C＃exception == 0 SQL [英] C# exception ==0 SQL

问题描述

我想将以下异常应用于我的脚本..

I would like to apply the following exception to my script..

ListBoxKlanten.Items.Count == 0

想法是当列表框ListBoxKlanten.Items.Count == 0将listBoxKlantenContact设为空白。 （有可能在listBoxKlantenContact中有准备好的记录）如何应用此异常以及我可以为此选项最好地使用哪些代码

The idea is that when the listbox "ListBoxKlanten.Items.Count == 0" that the "listBoxKlantenContact" is made blank. (it is possible that there ready records in "listBoxKlantenContact") How do I apply this exception and what code can I best use for this option

private void KlantenContactBOX()
{

    string queryKLantID = "SELECT IDKlantContactpersonen, FK_ID_Klant, Naam From Klantencontact WHERE FK_ID_Klant = @SELKlantID";

    using (connection = new SqlConnection(connectionstring))
    using (SqlCommand command = new SqlCommand(queryKLantID, connection))
    using (SqlDataAdapter adapter = new SqlDataAdapter(command))

    {
        command.Parameters.AddWithValue("@SELKlantID", ListBoxKlanten.SelectedValue);

        DataTable KlantenContactlijst = new DataTable();
        adapter.Fill(KlantenContactlijst);

            listBoxKlantenContact.DisplayMember = "Naam";
            listBoxKlantenContact.ValueMember = "IDKlantContactpersonen";
            listBoxKlantenContact.DataSource = KlantenContactlijst;
   }
}

推荐答案

问题解决了，谢谢你的帮助!!

Problem solved, Thank you for your help!!

if (ListBoxKlanten.Items.Count == 0)
               {
                   command.Parameters.AddWithValue("@SELKlantcontactinfoID", DBNull.Value);
               }
               else
               {
                   command.Parameters.AddWithValue("@SELKlantcontactinfoID", listBoxKlantenContact.SelectedValue);
               }

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