Dictionary

 Dictionary<int, string> moduleDetailInfo = new Dictionary<int, string>();

            IList<DynamicFormApplicationDataSource> moduleDetails = new DynamicFormApplicationDataSourceManager().GetModulesByModuleId(Convert.ToInt32(cmbModuleName.Value)).ToList();
            foreach (var moduleDetail in moduleDetails)
            {
                if (moduleDetail.IsPk)
                {
                    txtKeyField.Text = moduleDetail.Name;
                    txtKeyField.Tag = moduleDetail.Id;
                }
                else if (moduleDetail.DataType == "varchar")
                    moduleDetailInfo.Add(moduleDetail.Id, moduleDetail.Name);
            }
            cmbValueField.DataSource = new BindingSource(moduleDetailInfo, null);
            cmbValueField.ValueMember = "Key";
            cmbValueField.DisplayMember = "Value";