C#/ASP.NET gridview 数据绑定下拉列表索引已更改

Question

我是 .net 世界的新手，我不明白为什么下面的代码不起作用。我有一个下拉列表，其中包含 DEPARTMENT_NAME 和值作为 DEPARTMENT_ID。我有一个gridview，它根据从下拉列表中选择的department_id 填充员工数据。我已经编写了以下代码，但 gridview 没有填充。有人可以帮助我在这里做错了什么。

protected void ddDepartments_SelectedIndexChanged(object sender, EventArgs e)
        {
            string connStr = ConfigurationManager.ConnectionStrings["myCon"].ConnectionString;
            OracleConnection oConn = new OracleConnection(connStr);
            oConn.Open();
            string SqlText = "Select * from employees where department_id = :department_id";

            OracleCommand cmd = new OracleCommand(SqlText, oConn);
            cmd.CommandType = CommandType.Text;

            OracleParameter p_department_id = new OracleParameter();
            p_department_id.OracleDbType = OracleDbType.Varchar2;
            p_department_id.Value = ddDepartments.SelectedItem.Value;

            cmd.Parameters.Add(p_department_id); 

            OracleDataAdapter adapter = new OracleDataAdapter(cmd);
            DataTable dtEmployees = new DataTable();
            adapter.Fill(dtEmployees);

            gvEmployees.DataSource = dtEmployees;
            gvEmployees.DataBind();

            dtEmployees.Dispose();
            adapter.Dispose();
            cmd.Dispose();
            oConn.Close();
            oConn.Dispose();
        }

Answer 1

您需要使用 Session 变量将 gridView 数据源持久化到由下拉列表发送的 Postback 上。

那么紧接着：

gvEmployees.DataSource = dtEmployees;
gvEmployees.DataBind();

添加：

Session("gvDS") = gvEmployees.DataSource;

在页面Load()方法中：

if (Session["gvDS"] != null && IsPostBack)
{
    gvEmployees.DataSource = Session["gvDS"];
    gvEmployees.DataBind();
}
else
    BindGridView();  // you initial gvEmployees binding method

请看我的回答@：

Asp.net Web Forms GridView Dynamic Column Issue