ポストバック後にドロップダウンリストの選択値がリセットされます

Question

私はasp.netを初めて使用しており、ドロップダウンリストを修正するコードがいくつかあります。ユーザーが検索ボタンを押すと、選択した値がリセットされます。これで私を助けてくれますか？

これは

<fieldset> 
<legend>Search</legend> 

      <table class="tblsearch"> 
       <tr> 
        <td style="width:80px">Category:</td> 
        <td> 
         <asp:DropDownList ID="DDlistMainCat" runat="server" DataSourceID="sdmaincat" DataTextField="MainCategory" DataValueField="MainCategoryId" AutoPostBack="True"> 
         </asp:DropDownList> 
         <asp:SqlDataSource ID="sdmaincat" runat="server" ConnectionString="<%$ ConnectionStrings:CString %>" SelectCommand="SELECT * FROM [Tbl_MainCategory]"></asp:SqlDataSource> 
        </td> 
       </tr> 
       <tr> 
        <td>Sevices:</td> 
        <td> 
         <asp:DropDownList ID="DDlistCat" runat="server" DataSourceID="sdcat" DataTextField="Category" DataValueField="CategoryId"> 
         </asp:DropDownList> 
         <asp:SqlDataSource ID="sdcat" runat="server" ConnectionString="<%$ ConnectionStrings:CString %>" SelectCommand="SELECT [CategoryId], [Category] FROM [Tbl_Category] WHERE ([MainCategoryRef] = @MainCategoryRef)"> 
          <SelectParameters> 
           <asp:ControlParameter ControlID="DDlistMainCat" Name="MainCategoryRef" PropertyName="SelectedValue" Type="Int32" /> 
          </SelectParameters> 
         </asp:SqlDataSource> 
        </td> 
       </tr> 
      </table> 
    </fieldset> 
    <fieldset> 

    <table class="tblsearch"> 
       <tr> 
        <td style="width:80px">Nationality:</td> 
        <td> 
         <asp:DropDownList ID="DDlistNat" runat="server" DataSourceID="sdnat" DataTextField="Nationality" DataValueField="NationalityId" EnableViewState="true"> 
         </asp:DropDownList> 
         <asp:SqlDataSource ID="sdnat" runat="server" ConnectionString="<%$ ConnectionStrings:CString %>" SelectCommand="SELECT * FROM [Tbl_Nationality]"></asp:SqlDataSource> 
        </td> 
       </tr> 



      <tr> 
        <td>Age:</td> 
        <td> 
         <asp:DropDownList ID="DDlistAge" runat="server" DataSourceID="sdage" DataTextField="Age" DataValueField="AgeV"> 
         </asp:DropDownList> 
         <asp:SqlDataSource ID="sdage" runat="server" ConnectionString="<%$ ConnectionStrings:CString %>" SelectCommand="SELECT [AgeV], [Age] FROM [Tbl_Age]"></asp:SqlDataSource> 
        </td> 
       </tr> 
       <tr> 
        <td>Experience:</td> 
        <td> 
         <asp:DropDownList ID="DDlistExp" runat="server" DataSourceID="sdexp" DataTextField="Exp" DataValueField="ExpV"> 
         </asp:DropDownList> 
         <asp:SqlDataSource ID="sdexp" runat="server" ConnectionString="<%$ ConnectionStrings:CString %>" SelectCommand="SELECT [ExpV], [Exp] FROM [Tbl_Exp]" ></asp:SqlDataSource> 
        </td> 
       </tr> 
        <tr> 
        <td>Gender:</td> 
        <td> 
         <asp:DropDownList ID="DDlistGen" runat="server"> 
          <asp:ListItem>Male</asp:ListItem> 
          <asp:ListItem>Female</asp:ListItem> 
         </asp:DropDownList> 
         </td> 
       </tr> 
        <tr> 
        <td></td> 
        <td> 
         <asp:Button ID="BtnSearch" class="btn" runat="server" Text="Search" OnClick="BtnSearch_Click" /> 
         </td> 
       </tr> 
      </table> 



</fieldset> 

デザインのページであり、これはアクション

public partial class MasterPage : System.Web.UI.MasterPage 
{ 
    protected void Page_Load(object sender, EventArgs e) 
    { 
     if (Session["ClientId"] == null) 
     { 
      MyAccBox.Visible = false; 
     } 
     else 
     { 
      MyAccBox.Visible = true; 
      lblfullname.Text = Session["Fullname"].ToString(); 
     } 
    } 

    protected void BtnSearch_Click(object sender, EventArgs e) 
    { 
     Response.Redirect("View.aspx?cat=" + DDlistCat.SelectedValue + "&nat=" + DDlistNat.SelectedValue + "&age=" + DDlistAge.SelectedValue + "&exp=" + DDlistExp.SelectedValue + "&gen=" + DDlistGen.SelectedValue + ""); 
    } 
} 

Answer 1

これは、あなたが!IsPostBackに背後にあるコードからドロップダウンを結合した発生しないです。

if(!IsPostBack) 
{ 
DDlistExp.DataSource = DataSet.Tables[0];  
DDlistExp.DataValueField = "ExpV"; 
DDlistExp.DataTextField = "Exp"; 
DDlistExp.DataBind();  
}