c# - Oracle.DataAccess.dll 中出现“Oracle.DataAccess.Client.OracleException”类型的未处理异常

Question

我的代码有一个严重问题，当我尝试从表（通讯员）中检索 ID（号码）时总是抛出异常

        private void comboboxCorrespondant_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        #region connectDB

        OracleConnection con = new OracleConnection();
        con.ConnectionString = connectionString;
        con.Open();
        OracleCommand cmd = new OracleCommand();
        cmd.Connection = con;
        #endregion
        cmd.CommandText = " SELECT ID FROM CORRESPONDANT WHERE desingation = " + comboboxCorrespondant.SelectedItem.ToString();
        cmd.BindByName = true;
        object _id = cmd.ExecuteScalar();

        string returnId = _id.ToString();

        IdtextBox.Text = "";
        if (_id != null)
        {
            IdtextBox.Text = returnId;
        }

        con.Dispose();
        cmd.Dispose();

    }

标签： c#wpforacle11g