因此，我尝试为gridview添加多个过滤器，并用列的不同数据填充下拉列表，但它给了我一个异常system.argumentexception：在集合中找不到参数“sitevalue”。我添加了mysql存储过程和下面的代码。

<asp:GridView ID="gdvTM" runat="server" AutoGenerateColumns="False" AllowPaging="true" OnPageIndexChanging="gdvTM_PageIndexChanging" DataKeyNames="ID" PageSize="10" CssClass="cssgridview" AlternatingRowStyle-BackColor="#d5d8dc" >
 <Columns >
 <asp:TemplateField   HeaderText="Agent login">
 <ItemTemplate>
 <asp:Label ID="lbllogin" runat="server" Text='<%# Eval("agentlogin") %>'></asp:Label>
 </ItemTemplate>
 </asp:TemplateField>
 <asp:TemplateField >
 <HeaderTemplate>
  Site:
  <asp:DropDownList ID="ddlgvsite" runat="server" OnSelectedIndexChanged="DropDownChange" AutoPostBack="true" AppendDataBoundItems="true">
  </asp:DropDownList>
  </HeaderTemplate>
   <ItemTemplate>
   <asp:Label ID="lblsite" runat="server" Text='<%# Eval("site") %>'></asp:Label>
   </ItemTemplate>
   </asp:TemplateField>
   <asp:TemplateField>
   <HeaderTemplate>
    Skill:
    <asp:DropDownList ID="ddlgvskill" runat="server" OnSelectedIndexChanged="DropDownChange" AutoPostBack="true" AppendDataBoundItems="true">
     </asp:DropDownList>
     </HeaderTemplate>
     <ItemTemplate>
     <asp:Label ID="lblskill" runat="server" Text='<%# Eval("skill") %>'></asp:Label>
      </ItemTemplate>
      </asp:TemplateField>
      <asp:TemplateField HeaderText="Shift">
      <ItemTemplate>
      <asp:Label ID="lblshift" runat="server" Text='<%# Eval("shift") %>'></asp:Label>
      </ItemTemplate>
      </asp:TemplateField>
      <asp:TemplateField HeaderText="TM">
      <ItemTemplate>
      <asp:Label ID="lbltm" runat="server" Text='<%# Eval("tm") %>'></asp:Label>
      </ItemTemplate>
      </asp:TemplateField>
      <asp:TemplateField HeaderText="GrpM">
      <ItemTemplate>
      <asp:Label ID="lblGrpM" runat="server" Text='<%# Eval("grpM") %>'></asp:Label>
      </ItemTemplate>
      </asp:TemplateField>
      <asp:TemplateField HeaderText="OpsM">
      <ItemTemplate>
      <asp:Label ID="lblOpsM" runat="server" Text='<%# Eval("opsM") %>'></asp:Label>
      </ItemTemplate>
      </asp:TemplateField>
      <asp:TemplateField HeaderText="Leave type">
      <ItemTemplate>
      <asp:Label ID="lbltype" runat="server" Text='<%# Eval("leavetype") %>'></asp:Label>
      </ItemTemplate>
      </asp:TemplateField>
      <asp:TemplateField HeaderText="Date">
      <ItemTemplate >
      <asp:Label ID="lbldate" runat="server" Text='<%# Eval("date", "{0:dd/MM/yyyy}") %>'></asp:Label>
      </ItemTemplate>
      </asp:TemplateField>
     <asp:TemplateField HeaderText="Time">
     <ItemTemplate>
      <asp:Label ID="lbltime" runat="server" Text='<%# Eval("time") %>'></asp:Label>
     </ItemTemplate>
     </asp:TemplateField>
     <asp:TemplateField HeaderText="Reason" ControlStyle-Width="300px">
     <ItemTemplate>
     <asp:Label ID="lblreason" runat="server" Text='<%# Eval("reason") %>'></asp:Label>
     </ItemTemplate>
     </asp:TemplateField>
  </Columns>
 </asp:GridView>

下面是服务器端代码

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        BindGrid();
    }
}
private void BindDropDownList()
{
    TableCell cells = gdvTM.HeaderRow.Cells[0];
    PopulateDropDown((cells.FindControl("ddlgvsite") as DropDownList), (cells.FindControl("lblsite") as Label).Text);
    PopulateDropDown((cells.FindControl("ddlgvskill") as DropDownList), (cells.FindControl("lblskill") as Label).Text);

}

private void PopulateDropDown(DropDownList ddl, string columnName)
{
    ddl.DataSource = BindDropDown(columnName);
    ddl.DataTextField = columnName;
    ddl.DataValueField = columnName;
    ddl.DataBind();
    ddl.Items.Insert(0, new ListItem("Please Select", "0"));
}

private void BindGrid()
{
    DataTable dt = new DataTable();
    String strConnString = System.Configuration.ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;
    MySqlConnection con = new MySqlConnection(strConnString);
    MySqlDataAdapter sda = new MySqlDataAdapter();
    MySqlCommand cmd = new MySqlCommand("GetApprovedData");
    cmd.CommandType = CommandType.StoredProcedure;
    if (ViewState["Site"] != null && ViewState["Site"].ToString() != "0")
    {
        cmd.Parameters.AddWithValue("@siteValue", ViewState["Site"].ToString());
    }
    if (ViewState["Skill"] != null && ViewState["Skill"].ToString() != "0")
    {
        cmd.Parameters.AddWithValue("@skillValue", ViewState["Skill"].ToString());
    }
    cmd.Connection = con;
    sda.SelectCommand = cmd;
    sda.Fill(dt);
    gdvTM.DataSource = dt;
    gdvTM.DataBind();
    this.BindDropDownList();
    TableCell cell = gdvTM.HeaderRow.Cells[0];
    setDropdownselectedItem(ViewState["Site"] != null ? (string)ViewState["Site"] : string.Empty, cell.FindControl("ddlgvsite") as DropDownList);
    setDropdownselectedItem(ViewState["Skill"] != null ? (string)ViewState["Skill"] : string.Empty, cell.FindControl("ddlgvskill") as DropDownList);
}

private void setDropdownselectedItem(string selectedvalue, DropDownList ddl)
{
    if (!string.IsNullOrEmpty(selectedvalue))
    {
        ddl.Items.FindByValue(selectedvalue).Selected = true;
    }
}

protected void DropDownChange(object sender, EventArgs e)
{
    DropDownList dropdown = (DropDownList)sender;
    string selectedValue = dropdown.SelectedItem.Value;
    switch (dropdown.ID.ToLower())
    {
        case "ddlgvsite":
            ViewState["Site"] = selectedValue;
            break;
        case "ddlgvskill":
            ViewState["Skill"] = selectedValue;
            break;
    }
    this.BindGrid();
}

private DataTable BindDropDown(string columnName)
{
    String strConnString = System.Configuration.ConfigurationManager.ConnectionStrings["connStr"].ConnectionString;
    MySqlConnection con = new MySqlConnection(strConnString);
    MySqlCommand cmd = new MySqlCommand("SELECT DISTINCT " + columnName + " FROM approved WHERE " + columnName + " IS NOT NULL", con);
    MySqlDataAdapter sda = new MySqlDataAdapter(cmd);
    DataTable dt = new DataTable();
    sda.Fill(dt);
    return dt;
}
protected void gdvTM_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
    gdvTM.PageIndex = e.NewPageIndex;
    this.BindGrid();
}

下面是mysql存储过程

CREATE DEFINER=`root`@`localhost` PROCEDURE `GetApprovedData`
(in  siteValue varchar(45), in skillValue varchar(100))
BEGIN
    select *
    from approved
    where site = siteValue or siteValue is null and 
          skill = skillValue or skillValue is null;
END

请让我知道我做错了什么。提前谢谢。。。。