Bind a DropDown in ListView in Edit & Insert Templ

问题:

In my ASP.NET 4.5 WebForms app, In my ListView I am trying to bind DropDownList, but am not able to do it. Actually, the Model that is bind to ListView, has a Property of UnitdirectionId & on Edit & Insert Templates' I want to show the dropdown of all UnitDirection table.

Here is my EditTempalte :

    <EditItemTemplate>
           <tr>
               <td>
                   <asp:TextBox ID="unitDirTxt" runat="server" Text='<%# Bind("UnitDirectionId") %>'></asp:TextBox>
                    <!-- <asp:DynamicControl runat="server" DataField="UnitDirectionId" ID="UnitDirectionId" Mode="Edit" />  -->
                   <asp:DropDownList ID="unitDirEditDrop" runat="server" ItemType="VincitoreCRMApplication.Models.UnitDirection"
                       DataTextField="DirectionTitle" DataValueField="UnitDirectionId" 
                       SelectMethod="GetUnitDirections"></asp:DropDownList>  
               </td> 
          </tr>

        </EditItemTemplate>

In Code behind,

    public IQueryable<UnitDirection> GetUnitDirections()
    {
        return _db.UnitDirections;
    }

Now, the Model of LsitView has the proerpty as follows :

    [Display(Name= "Unit Direction")]
    public int UnitDirectionId { get; set; }

    [ForeignKey("UnitDirectionId")]
    public virtual UnitDirection UnitDirection { get; set; }

Now, the UnitDirection Model :

public class UnitDirection
{
    [ScaffoldColumn(false)]
    public int UnitDirectionId { get; set; }

    [Required]
    [Display]
    public string DirectionTitle { get; set; }
}

ERROR that I get is :

 ########## ERRO : An error occurred while executing the command definition. See the inner exception for details. 
 STACK :    at   System.Data.Entity.Core.EntityClient.Internal.EntityCommandDefinition.ExecuteSto reCommands(EntityCommand entityCommand, CommandBehavior behavior)
  at   System.Data.Entity.Core.Objects.Internal.ObjectQueryExecutionPlan.Execute[TResul    tType](ObjectContext context, ObjectParameterCollection parameterValues)
  at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__6()
  at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.<>c__DisplayClass7.<GetResults>b__5()
   at System.Data.Entity.SqlServer.DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)
   at System.Data.Entity.Core.Objects.ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
  at System.Data.Entity.Core.Objects.ObjectQuery`1.<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0()
  at System.Data.Entity.Internal.LazyEnumerator`1.MoveNext()
  at System.Web.UI.WebControls.ListControl.PerformDataBinding(IEnumerable dataSource)
  at System.Web.UI.WebControls.ListControl.OnDataBinding(EventArgs e)
  at System.Web.UI.WebControls.ListControl.PerformSelect()
  at System.Web.UI.WebControls.BaseDataBoundControl.DataBind()
  at System.Web.UI.Control.DataBindChildren()
  at System.Web.UI.Control.DataBind(Boolean raiseOnDataBinding)
  at System.Web.UI.Control.DataBind()
  at System.Web.UI.WebControls.ListView.CreateItemsWithoutGroups(ListViewPagedDataSource dataSource, Boolean dataBinding, InsertItemPosition insertPosition, ArrayList keyArray)
  at System.Web.UI.WebControls.ListView.CreateChildControls(IEnumerable dataSource, Boolean dataBinding)
  at System.Web.UI.WebControls.ListView.PerformDataBinding(IEnumerable data)
  at System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data)
  at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback)
   at System.Web.UI.WebControls.DataBoundControl.PerformSelect()
  at System.Web.UI.WebControls.ListView.PerformSelect()
  at System.Web.UI.WebControls.BaseDataBoundControl.DataBind()
  at System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound()
  at System.Web.UI.WebControls.BaseDataBoundControl.OnPreRender(EventArgs e)
  at System.Web.UI.Control.PreRenderRecursiveInternal()
  at System.Web.UI.Control.PreRenderRecursiveInternal()
  at System.Web.UI.Control.PreRenderRecursiveInternal()
  at System.Web.UI.Control.PreRenderRecursiveInternal()
  at System.Web.UI.Control.PreRenderRecursiveInternal()
  at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

In db the UnitDirection table has 3 items.

With the above drop down, I believe I should atleast get list of all UnitDirection in drop down. But on that I am getting error. Then comes to set the selected item in Edit Template.

Can you please help me identify why I am getting this error ?? Any help is highly appreciated.

Thanks

回答1:

As we discuss in the stackoverflow chat, you are facing below error in your drop down binding method.

System.InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.

Please add MultipleActiveResultSets=true in your web.config connection string to solve your problem.

Server=.\SQLEXPRESS;Database=master;Integrated Security=SSPI;
MultipleActiveResultSets=true;

For fetch you UnitDirection value, you need to write one method like below and return UnitDirection title as return type.

public string getUnitDirectionTitle(int fiUnitDirectionId)
{
    return UnitDirection.Where(c => c.UnitDirectionId == fiUnitDirectionId);
}

after that call above method in your ItemDataBound event,

TextBox.Text = getUnitDirectionTitle(loItem.UnitDirectionId);

Please let me know if you have any questions.