Pourquoi est-ce que je reçois une erreur de référence d'objet NULL lors de l'enregistrement (premier événement OnItemUpdating) du premier élément de modification dans un ListView?

Question

Je reçois le message d'erreur "Référence d'objet non définie sur une instance d'objet". lors de la tentative de référence à un objet HiddenField (lvEditProjectSteps_hdnStepStatusId pour une référence future) à partir de EditItem pendant l'événement OnItemUpdating après que l'événement Update se soit déclenché dans un ListView. Cela se produit uniquement sur l'élément FIRST dans ListView. J'ai vérifié le code source et le code HTML est correctement rendu.

Toute idée est appréciée! Merci d'avance ...

Erreur source:

var lvEditProjectSteps_hdnStepStatusId = (HiddenField) lvEditProjectSteps.EditItem.FindControl("lvEditProjectSteps_hdnStepStatusId");

Voici le côté aspx de ListView:

<asp:ListView ID="lvEditProjectSteps" runat="server"
  OnItemDataBound="lvEditProjectSteps_OnItemDataBound" 
  OnItemUpdating="lvEditProjectSteps_OnItemUpdating" 
  DataSourceID="odsEditProjectStep" 
  DataKeyNames="Id">
  <LayoutTemplate>
    <table class="standard-box-style" style="width:800px">
      <thead>
        <tr>
          <th>&nbsp;</th>
          <th>&nbsp;</th>
          <th>Created</th>
          <th>Updated</th>
        </tr>
      </thead>
      <tbody>
        <asp:PlaceHolder ID="itemPlaceHolder" runat="server" />
      </tbody>
    </table>
  </LayoutTemplate>
  <ItemTemplate>
    <tr>
      <td style="width:50px"<%# (Container.DisplayIndex % 2 == 0)?"":" class=\"row-alternating\"" %>>
        <asp:ImageButton ID="lvEditProjectSteps_btnEdit" runat="server" 
          ImageUrl="~/admin/images/icons/edit.gif" 
          AlternateText="Edit" 
          SkinID="interfaceButton"
          CommandName="Edit" />
        <asp:HiddenField ID="lvEditProjectSteps_hdnId" runat="server" Value='<%# Bind("Id")%>' />
        <asp:HiddenField ID="lvEditProjectSteps_hdnStepStatusId" runat="server" Value='<%# Bind("StepStatusId")%>' />
        <asp:HiddenField ID="lvEditProjectSteps_hdnStepStatusStepId" runat="server" Value='<%# Bind("StepStatus_StepId")%>' />
      </td>
      <td style="width:30px"<%# (Container.DisplayIndex % 2 == 0)?"":" class=\"row-alternating\"" %>><asp:Image ID="imgStatus" runat="server" /></td>
      <td style="width:75px"<%# (Container.DisplayIndex % 2 == 0)?"":" class=\"row-alternating\"" %>><asp:Literal ID="litTsCreated" runat="server" /></td>
      <td style="width:75px"<%# (Container.DisplayIndex % 2 == 0)?"":" class=\"row-alternating\"" %>><asp:Literal ID="litTsUpdated" runat="server" /></td>
    </tr>
  </ItemTemplate>
  <EditItemTemplate>
    <tr>
      <td style="width:50px"<%# (Container.DisplayIndex % 2 == 0)?"":" class=\"row-alternating\"" %>>
        <asp:ImageButton ID="lvEditProjectSteps_btnUpdate" runat="server" 
          ImageUrl="~/admin/images/icons/save.png" 
          AlternateText="Save" 
          SkinID="interfaceButton"
          CommandName="Update" 
          ValidationGroup="EditProjectStepsSave" />
        <asp:ImageButton ID="lvEditProjectSteps_btnCancel" runat="server" 
          ImageUrl="~/admin/images/icons/cancel.png" 
          AlternateText="Cancel" 
          SkinID="interfaceButton"
          CommandName="Cancel" />
        <asp:HiddenField ID="lvEditProjectSteps_hdnId" runat="server" Value='<%# Bind("Id")%>' />
        <asp:HiddenField ID="lvEditProjectSteps_hdnStepStatusId" runat="server" Value='<%# Bind("StepStatusId")%>' />
        <asp:HiddenField ID="lvEditProjectSteps_hdnStepStatusStepId" runat="server" Value='<%# Bind("StepStatus_StepId")%>' />
      </td>
      <td style="width:180px" colspan="3"<%# (Container.DisplayIndex % 2 == 0)?"":" class=\"row-alternating\"" %>>
        <div><strong>Status</strong></div>
        <div class="radiobuttonlist-status">
          <asp:RadioButtonList ID="lvEditProjectSteps_rblStatus" runat="server"     
            RepeatDirection="Horizontal"    
            AutoPostBack="true"
            OnSelectedIndexChanged="lvEditProjectSteps_rblStatus_OnSelectedIndexChanged">
            <asp:ListItem Value="1"><img src="/images/icon/project-status/1.png" alt="Error" /></asp:ListItem>
            <asp:ListItem Value="2"><img src="/images/icon/project-status/2.png" alt="In Progress" /></asp:ListItem>
            <asp:ListItem Value="3"><img src="/images/icon/project-status/3.png" alt="Complete" /></asp:ListItem>
          </asp:RadioButtonList>
          <asp:RequiredFieldValidator ID="valRequired_lvEditProjectSteps_rblStatus" runat="server" 
            ControlToValidate="lvEditProjectSteps_rblStatus" 
            SetFocusOnError="true"
            Display="Dynamic" 
            ErrorMessage="<br />^ required ^" 
            ValidationGroup="EditProjectStepsSave" />
        </div>
      </td>
    </tr>
  </EditItemTemplate>
</asp:ListView>

Et le code-behind:

protected void lvEditProjectSteps_OnItemDataBound(object sender, ListViewItemEventArgs e)
{
  if (e.Item.ItemType == ListViewItemType.DataItem)
  {
    var info = (ProjectStepInfo)DataBinder.GetDataItem(e.Item);

    // View Item
    var litTsCreated = (Literal)e.Item.FindControl("litTsCreated");
    var litTsUpdated = (Literal)e.Item.FindControl("litTsUpdated");
    var imgStatus = (Image) e.Item.FindControl("imgStatus");

    if (litTsCreated != null) litTsCreated.Text = String.Format("{0:d}", info.TsCreated);
    if (litTsUpdated != null) litTsUpdated.Text = String.Format("{0:d}", info.TsCreated);
    if (imgStatus != null) imgStatus.ImageUrl = String.Format("/images/icon/project-status/{0}.png", info.StepStatus_StatusId);

    // Edit Item
    var lvEditProjectSteps_rblStatus = (RadioButtonList) e.Item.FindControl("lvEditProjectSteps_rblStatus");
    if (lvEditProjectSteps_rblStatus != null) lvEditProjectSteps_rblStatus.SelectedValue = info.StepStatus_StatusId.ToString();
  }
}
protected void lvEditProjectSteps_OnItemUpdating(object sender, ListViewUpdateEventArgs e)
{
  if (IsValid)
  {
    var oController = new Controller();
    var lvEditProjectSteps_hdnStepStatusId = (HiddenField) lvEditProjectSteps.EditItem.FindControl("lvEditProjectSteps_hdnStepStatusId");
    var lvEditProjectSteps_hdnStepStatusStepId = (HiddenField) lvEditProjectSteps.EditItem.FindControl("lvEditProjectSteps_hdnStepStatusStepId");
    var lvEditProjectSteps_rblStatus = (RadioButtonList) lvEditProjectSteps.EditItem.FindControl("lvEditProjectSteps_rblStatus");
    var infoStepStatus = oController.StepStatus_SelectOne_StepId_StatusId(Convert.ToInt32(lvEditProjectSteps_hdnStepStatusStepId.Value), Convert.ToInt32(lvEditProjectSteps_rblStatus.SelectedValue));
    if (lvEditProjectSteps_hdnStepStatusId != null)
    {
      e.NewValues["ProjectId"] = Convert.ToInt32(lvEditProjectSteps_hdnProjectId.Value);
      e.NewValues["StepStatusId"] = infoStepStatus.Id;
    }
    else
    {
      Response.Write("cancel");
      e.Cancel = true;
    }
  }
  else
  {
    Response.Write("cancel, not valid");
    e.Cancel = true;
  }
}
protected void lvEditProjectSteps_rblStatus_OnSelectedIndexChanged(object sender, EventArgs e)
{
  var oController = new Controller();
  var rbl = (RadioButtonList)sender;
  var lvEditProjectSteps_txtText = (TextBox) rbl.NamingContainer.FindControl("lvEditProjectSteps_txtText");
  var lvEditProjectSteps_txtComment = (TextBox)rbl.NamingContainer.FindControl("lvEditProjectSteps_txtComment");
  var lvEditProjectSteps_hdnStepStatusStepId = (HiddenField) rbl.NamingContainer.FindControl("lvEditProjectSteps_hdnStepStatusStepId");
  if (!String.IsNullOrEmpty(lvEditProjectSteps_hdnStepStatusStepId.Value) && lvEditProjectSteps_txtText != null && lvEditProjectSteps_txtComment != null)
  {
    var infoStep = oController.Step_SelectOne(Convert.ToInt32(lvEditProjectSteps_hdnStepStatusStepId.Value));
    var infoStepStatus = oController.StepStatus_SelectOne_StepId_StatusId(Convert.ToInt32(lvEditProjectSteps_hdnStepStatusStepId.Value), Convert.ToInt32(rbl.SelectedValue));

    lvEditProjectSteps_txtText.Text = infoStep.Name;
    lvEditProjectSteps_txtComment.Text = infoStepStatus.Text;
  }
}

Answer 1

J'ai résolu mon propre problème. Il semble y avoir un bogue lors de la sélection d’un Edit ListViewItem comme ceci (en utilisant l’exemple ci-dessus):

lvEditProjectSteps.EditItem

mais pas lorsque vous utilisez cette méthode:

lvEditProjectSteps.Items[lvEditProjectSteps.EditIndex]

espérons que cela aide quelqu'un d'autre.