LinqDataSource：篩選並綁定到gridview

Question

這個問題沒有按照我想要的方式解決，但是我繼續感謝ŁukaszW.pl的時間和精力。

我正在使用gridview控件和linqdatasource及其所有工作正常，我已經添加了searchBySubject的功能，並且添加了WhereParameters，而不是綁定我的gridview（請參見下面的代碼），但是不知何故，它不返回任何行，我看到我有很多根據我搜索的行。

 protected void btnSearch_Click(object sender, EventArgs e)
 {    
   this.LinqDataSource1.WhereParameters["Subject"].DefaultValue = this.txtSubject.Text;
   this.GridView1.DataBind();
 }

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"  
         DataSourceID="LinqDataSource1"  
        EmptyDataText="There are no data records to display."> 
        <Columns> 
            <asp:BoundField DataField="UserID" HeaderText="UserID" ReadOnly="True"  
                SortExpression="UserID" /> 
            <asp:BoundField DataField="Username" HeaderText="Username"  
                SortExpression="Username" /> 
            <asp:BoundField DataField="FirstName" HeaderText="FirstName"  
                SortExpression="FirstName" /> 
            <asp:BoundField DataField="LastName" HeaderText="LastName"  
                SortExpression="LastName" /> 
            <asp:BoundField DataField="Email" HeaderText="Email" SortExpression="Email" /> 
        </Columns> 
    </asp:GridView> 

     <asp:LinqDataSource ID="LinqDataSource1" runat="server"  
        ContextTypeName="MyDataContextDataContext" 
        onselecting="LinqDataSource_Selecting" > 
            <WhereParameters> 
               <asp:Parameter Name="Subject" />
            </WhereParameters> 
        </asp:LinqDataSource>



public List<Reporter> GetInquiries()
        {
            using (MyDataContextDataContext dc = conn.GetContext())
            {
                var loadAll = (from spName in dc.spReporter()
                               select spName);

                List<Reporter> reporterList = new List<Reporter>();

                foreach (var item in loadAll)
                {
                    reporterList.Add(new Reporter(item.Id, item.InqDate, item.Subject));
                }                

                return reporterList;
            }      

錯誤：

 The query results cannot be enumerated more than once

Answer 1

假設您在頁面中聲明了這樣的LinqDataSource ：

<asp:LinqDataSource ID="LinqDataSource1"
                    runat="server"  
                    ContextTypeName="MyDataContext"
                    OnSelecting="LinqDataSource1_Selecting">
    <WhereParameters>
        <asp:ControlParameter Name="Subject"
                              ControlID="txtSubject"
                              PropertyName="Text"
                              Type="String" />
    </WhereParameters>
</asp:LinqDataSource>

您的LinqDataSource.Selecting事件處理程序應大致如下所示：

public void LinqDataSource1_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
     var db = new MyDataContext())
     var subjectFilter = e.WhereParameters("Subject");
     var reporters = from spName in db.spReporter()
                     where spName.Subject.Contains(subjectFilter)
                     select new Reporter(spName.Id, spName.InqDate, spName.Subject);
     e.Result = reporters;
}

或者，您可以將“主題”作為輸入參數添加到存儲過程和數據庫中的過濾中。 在這種情況下，事件處理程序將如下所示：

public void LinqDataSource1_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{
     var db = new MyDataContext())
     var subjectFilter = e.WhereParameters("Subject");
     var reporters = from spName in db.spReporter(subjectFilter)
                     select new Reporter(spName.Id, spName.InqDate, spName.Subject);
     e.Result = reporters;
}

相關資源：

• LinqDataSource-使用存儲過程

Answer 2

關於該問題，我看不到您的GetInquiries方法和LinqDataSource之間的任何連接。 那就是第一，第二是即使有連接，如果您要返回列表而不是IQueriable對象，它也將無法工作...

為了更好地了解與LinqDataSource的綁定，請閱讀此Scott Gu的文章

我還要向您展示可以將您的GetInquiries方法簡化為以下形式：

    public List<Reporter> GetInquiries()
    {
        using (MyDataContextDataContext dc = conn.GetContext())
        {
            return (from spName in dc.spReporter()
                    select new Reporter(spName.Id, spName.InqDate, spName.Subject)).ToList()

        }      

----編輯----

替代解決方案的示例：

    public List<Reporter> GetInquiries(string subject)
    {
        using (MyDataContextDataContext dc = conn.GetContext())
        {
            return (from spName in dc.spReporter()
                    select new Reporter(spName.Id, spName.InqDate, spName.Subject
                    where spName.Subject == subject)).ToList()

        }  
    }

    protected void btnSearch_Click(object sender, EventArgs e)
    {    
       GridView1.DataSource = GetInquiries(txtSubject.Text);
       GridView1.DataBind();
    }

----------編輯-------------

protected void btnSearch_Click(object sender, EventArgs e)
{    
   this.LinqDataSource1.WhereParameters["Subject"].DefaultValue = this.txtSubject.Text;
   this.GridView1.DataBind();
}

public void LinqDataSource1_Selecting(object sender, LinqDataSourceSelectEventArgs e)
{ 
    ReporterRepository reporterRepo = new ReporterRepository();
    e.Result = reporterRepo.GetInquiries();    
}

public IQueryable<Reporter> GetInquiries()
{
    return from spName in dc.spReporter()
           select new Reporter(spName.Id, spName.InqDate, spName.Subject);
}     

<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="LinqDataSource1" EmptyDataText="There are no data records to display."> 
        <Columns> 
            <asp:BoundField DataField="UserID" HeaderText="UserID" ReadOnly="True"  
                SortExpression="UserID" /> 
            <asp:BoundField DataField="Username" HeaderText="Username"  
                SortExpression="Username" /> 
            <asp:BoundField DataField="FirstName" HeaderText="FirstName"  
                SortExpression="FirstName" /> 
            <asp:BoundField DataField="LastName" HeaderText="LastName"  
                SortExpression="LastName" /> 
            <asp:BoundField DataField="Email" HeaderText="Email" SortExpression="Email" /> 
        </Columns> 
</asp:GridView> 

<asp:LinqDataSource ID="LinqDataSource1" runat="server" ContextTypeName="MyDataContextDataContext" onselecting="LinqDataSource_Selecting"> 
        <WhereParameters> 
           <asp:Parameter Name="Subject" />
        </WhereParameters> 
</asp:LinqDataSource>

問候