指定的转换是无效的消息在asp.net上RowFilter

在asp.net网站使用c＃时，我试图从数据库表中的下拉列表中获取产品列表产品我收到调试消息“指定演员不是有效”。任何人都可以指出错误？请它真的很紧急。指定的转换是无效的消息在asp.net上RowFilter

这里是我的堆栈跟踪：

[InvalidCastException: Specified cast is not valid.] 
    Order.GetSelectedProduct() +371 
    Order.Page_Load(Object sender, EventArgs e) +40 
    System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14 
    System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +44 
    System.Web.UI.Control.OnLoad(EventArgs e) +83 
    System.Web.UI.Control.LoadRecursive() +120 
    System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3955

Order.aspx.cs：

public partial class Order : System.Web.UI.Page 
{ 

    private Product selectedProduct; 

    protected void Page_Load(object sender, EventArgs e) 
    { 
     if (!IsPostBack) 
      ddlProducts.DataBind(); 
     selectedProduct = this.GetSelectedProduct(); 
     lblName.Text = selectedProduct.Name; 
     lblShortDescription.Text = selectedProduct.ShortDescription; 
     lblLongDescription.Text = selectedProduct.LongDescription; 
     lblUnitPrice.Text = selectedProduct.UnitPrice.ToString("c"); 
     imgProduct.ImageUrl = "Images/Products/" + selectedProduct.ImageFile; 
    } 




    private Product GetSelectedProduct() 
    { 
     DataView productsTable = (DataView) 
      SqlDataSource2.Select(DataSourceSelectArguments.Empty); 
     productsTable.RowFilter = "P_Id = '" + ddlProducts.SelectedValue + "'"; 
     DataRowView row = (DataRowView)productsTable[0]; 
     Product p = new Product(); 
     p.ProductID = row["P_Id"].ToString(); 
     p.Name = row["Title"].ToString(); 
     p.ShortDescription = row["Desc"].ToString(); 
     p.LongDescription = row["Desc_full"].ToString(); 
     p.UnitPrice = (decimal)row["Price"]; 
     p.ImageFile = row["P_image"].ToString(); 
     return p; 
    } 
    protected void btnAdd_Click(object sender, EventArgs e) 
    { 

     if (Page.IsValid) 
     { 
      CartItem item = new CartItem(); 
      item.Product = selectedProduct; 
      item.Quantity = 1; 
      this.AddToCart(item); 
      Response.Redirect("Cart.aspx"); 
     } 

    } 


    private void AddToCart(CartItem item) 
    { 
     SortedList cart = this.GetCart(); 
     string productID = selectedProduct.ProductID; 
     if (cart.ContainsKey(productID)) 
     { 
      CartItem existingItem = (CartItem)cart[productID]; 
      existingItem.Quantity += 1; 
     } 
     else 
      cart.Add(productID, item); 
    } 


    private SortedList GetCart() 
    { 
     if (Session["Cart"] == null) 
      Session.Add("Cart", new SortedList()); 
     return (SortedList)Session["Cart"]; 
    } 
}

Order.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Order.aspx.cs" Inherits="Order" %> 

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 

<html xmlns="http://www.w3.org/1999/xhtml"> 
<head runat="server"> 
    <title>Welcome to LetsDressUp</title> 
</head> 
<body> 
    <form id="form1" runat="server"> 
    <div> 

    Please select a product: 
     <br /> 

     <asp:DropDownList ID="ddlProducts" runat="server" 
      DataSourceID="SqlDataSource2" DataTextField="Title" DataValueField="P_Id"> 
      <asp:ListItem></asp:ListItem> 
     </asp:DropDownList> 
     <asp:SqlDataSource ID="SqlDataSource2" runat="server" 
      ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
      SelectCommand="SELECT [P_Id], [Title], [Desc], [Desc_full], [Price], [P_image] FROM [Product]"> 
     </asp:SqlDataSource> 
     <asp:SqlDataSource ID="SqlDataSource1" runat="server" 
      ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
      SelectCommand="SELECT * FROM [Product]" 
      onselecting="SqlDataSource1_Selecting"></asp:SqlDataSource> 
     <br /> 

     <table> 
     <tr> 


     <td class="style1"> 
        <asp:Label ID="lblName" runat="server" 
         style="font-weight: 700; font-size: larger"> 
        </asp:Label> 
       </td> 
       <td class="style2" rowspan="4"> 
       </td> 
       <td rowspan="4" valign="top"> 
        <asp:Image ID="imgProduct" runat="server" Height="200px" /> 
       </td> 

     </tr> 

     <tr> 
       <td class="style1"> 
        <asp:Label ID="lblShortDescription" runat="server"> 
        </asp:Label> 
       </td> 
      </tr> 
      <tr> 
       <td class="style1"> 
        <asp:Label ID="lblLongDescription" runat="server"> 
        </asp:Label> 
       </td> 
      </tr> 
      <tr> 
       <td class="style1"> 
        <asp:Label ID="lblUnitPrice" runat="server" 
         style="font-weight: 700; font-size: larger"> 
        </asp:Label> 
        <asp:Label ID="Label2" runat="server" Text="each" 
         style="font-weight: 700; font-size: larger"> 
        </asp:Label> 
       </td> 
      </tr> 


     </table> 

     <asp:Button ID="btnAdd" runat="server" onclick="btnAdd_Click" 
      Text="Add to Cart" /> 
&nbsp;<asp:Button ID="btnCart" runat="server" PostBackUrl="~/Cart.aspx" 
      Text="Go to Cart" /> 
    </div> 
    </form> 
</body> 
</html>

感谢您的帮助。

来源

2013-10-12 user2011302

你几乎能够得到您所需要的所有信息在堆栈跟踪中。问题出在'GetSelectedProduct'方法中。特别是在该代码隐藏文件中查看第371行。 –

我应该如何将dataview转换为datarowview？我究竟做错了什么？ – user2011302

您可以使用foreach循环访问dataview对象的行。

foreach (DataRowView rowView in productsTable) 
{ 
    DataRow row = rowView.Row; 
    // Do something with the row // 

    // and if you just wanted to process the first record 
    // use break to end the loop 
    break; 
}

或者你可以使用FirstOrDefault扩展方法得到公正的第一行，类似于你试图在你的方法做

DataRowView rowView = productsTable.FirstOrDefault<DataRowView>()

来源

2013-10-12 21:25:32

它的工作，谢谢！ – user2011302

指定的转换是无效的消息在asp.net上RowFilter

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