如何檢查ListItem是否被選中？

Question

我正在做一個迷你測驗，我被困在C＃編碼中，檢查用戶從DropDownList中選擇哪個ListItem。

  <li><b>What is 231 mod 55?</b> 
       <asp:Label ID="lblQuestionResult2" runat="server" Font-Bold="true" Font-Size="16px" /> 
       <br /> 
       <asp:DropDownList ID="DropDownList1" runat="server" Width="55px"> 
        <asp:ListItem>14</asp:ListItem> 
        <asp:ListItem>6</asp:ListItem> 
        <asp:ListItem>11</asp:ListItem> 
       </asp:DropDownList> 
      </li> 

我沒有工作。如何去檢查用戶選擇的內容？

if (ListItem.Equals(toString(11))) 
    { 
     lblQuestionResult2.ForeColor = System.Drawing.Color.Green; 
     lblQuestionResult2.Text = "Correct"; 
    } 
    else 
    { 
     lblQuestionResult2.ForeColor = System.Drawing.Color.Red; 
     lblQuestionResult2.Text = "Incorrect"; 
    } 

Answer 1

你DropDownList控制已經是一個服務器側面控制。爲OnSelectedIndexChanged事件添加事件處理程序並對其進行處理。它應該看起來像

<asp:DropDownList ID="DropDownList1" 
     runat="server" Width="55px" AutoPostBack="true" 
     OnSelectedIndexChanged="OnComboSelectionChanged"> 

在後面的代碼，你可以添加這樣

protected void OnComboSelectionChanged(object sender, EventArgs e) 
{ 
    // Your code goes here. 
    string selectedValue = DropDownList1.SelectedValue; 

} 

處理程序請確保您使用

AutoPostBack="true" 

Answer 2

有兩種方式來得到它：

//One way 
string selectedvalue = ddList.SelectedValue; 

//Second Way 
string selectedindex = ddList.SelectedItem.Text; 

的完整的例子：

我已經推杆一個DropDownList和Button

<asp:DropDownList ID="ddList" runat="server"> 
     <asp:ListItem>14</asp:ListItem> 
     <asp:ListItem>6</asp:ListItem> 
     <asp:ListItem>11</asp:ListItem> 
</asp:DropDownList> 

<asp:Button ID="btnClick" runat="server" Text="Button" OnClick="btnClick_Click" /> 

，我開了一個方法當用戶點擊按鈕時觸發這些按鈕

protected void btnClick_Click(object sender, EventArgs e) 
{ 

    string selectedvalue = ddList.SelectedValue; 
    string selectedindex = ddList.SelectedItem.Text; 
} 

Answer 3

此MSDN頁面應該有所幫助。看起來你需要做 http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listitem.selected.aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-2

Answer 4

這是什麼可以幫助你

// ASPX側

<asp:DropDownList ID="DropDownList1" runat="server" Width="55px" 
        onselectedindexchanged="DropDownList1_SelectedIndexChanged"> 
        <asp:ListItem>14</asp:ListItem> 
        <asp:ListItem>6</asp:ListItem> 
        <asp:ListItem>11</asp:ListItem> 
       </asp:DropDownList> 

// CS側

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) 
    { 
     if (DropDownList1.SelectedValue=="11") 
     { 
      lblQuestionResult2.ForeColor = System.Drawing.Color.Green; 
      lblQuestionResult2.Text = "Correct"; 
     } 
     else 
     { 
      lblQuestionResult2.ForeColor = System.Drawing.Color.Red; 
      lblQuestionResult2.Text = "Incorrect"; 
     } 
    } 

Answer 5

<asp:DropDownList ID="DropDownList1" runat="server" Width="55px" 
       onselectedindexchanged="DropDownList1_SelectedIndexChanged"> 
       <asp:ListItem>14</asp:ListItem> 
       <asp:ListItem>6</asp:ListItem> 
       <asp:ListItem>11</asp:ListItem> 
      </asp:DropDownList> 

//背後

代碼

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) 
{ 
    if (DropDownList1.SelectedIndex!=0) 
    { 
     //your code implementation for selected value 
    } 
}