我想知道是否有人可以帮助我。我一直在寻找答案，到目前为止，但我想我错过了什么。
我有一个使用动态数据创建的FormView。在那个FormView中我有3个字段，ItemCosts，AdditionalCosts和TotalCosts。我希望能够在表单上放置一个按钮，将ItemsCosts和AdditionalCosts添加到一起，并将其显示在TotalCosts文本框中。很简单......所以我想。
我发现我需要使用ItemCommand，因为FormView在回发时会使用此命令。这就是我写的：
HTML
<asp:Panel ID="DetailsPanel" runat="server">
<br /><br />
<asp:FormView ID="FormView1" runat="server" DataSourceID="DetailsDataSource" RenderOuterTable="false"
OnPreRender="FormView1_PreRender" OnModeChanging="FormView1_ModeChanging" OnItemUpdated="FormView1_ItemUpdated"
OnItemInserted="FormView1_ItemInserted" OnItemDeleted="FormView1_ItemDeleted" OnItemCommand="FormView1_ItemCommand" OnDataBinding="FormView1_DataBind">
<HeaderTemplate>
<table id="detailsTable" class="DDDetailsTable" cellpadding="6">
</HeaderTemplate>
<ItemTemplate>
<tr class="td">
<td class="DDLightHeader">Order No</td>
<td><asp:DynamicControl ID="OrderNo" runat="server" DataField="OrderNo" /></td>
</tr>
<tr class="td">
<td class="DDLightHeader">Item Costs</td>
<td><asp:DynamicControl runat="server" DataField="ItemCosts" /></td>
</tr>
<tr class="td">
<td class="DDLightHeader">AdditionalCosts</td>
<td><asp:DynamicControl runat="server" DataField="AdditionalCosts" /></td>
</tr>
<tr class="td">
<td class="DDLightHeader">Total Costs</td>
<td><asp:DynamicControl runat="server" DataField="TotalCosts" /></td>
</tr>
<tr class="td">
<td colspan="2">
<asp:LinkButton ID="LinkButton1" runat="server" CommandName="Edit" Text="Edit" />
<asp:LinkButton ID="LinkButton2" runat="server" CommandName="Delete" Text="Delete"
OnClientClick='return confirm("Are you sure you want to delete this item?");' />
</td>
</tr>
</ItemTemplate>
<EditItemTemplate>
<tr class="td">
<td class="DDLightHeader">Order No</td>
<td><asp:DynamicControl ID="OrderNo" runat="server" DataField="OrderNo" Mode="ReadOnly"/></td>
</tr>
<tr class="td">
<td class="DDLightHeader">Item Costs</td>
<td><asp:DynamicControl runat="server" DataField="ItemCosts" Mode="Edit" /></td>
</tr>
<tr class="td">
<td class="DDLightHeader">Additional Costs</td>
<td><asp:DynamicControl runat="server" DataField="AdditionalCosts" Mode="Edit" /></td>
</tr>
<tr class="td">
<td class="DDLightHeader">Total Costs</td>
<td><asp:DynamicControl runat="server" DataField="TotalCosts" Mode="Edit" /></td>
<td><asp:Button runat="server" ID="btnCalculateTotalCosts" Text="Calculate total costs" CommandName="Calculate" /></td>
</tr>
<tr class="td">
<td class="DDLightHeader">View Items</td>
<td><asp:DynamicControl runat="server" DataField="tblCateringOrdersDetailsItems" Mode="Edit" /></td>
</tr>
<tr class="td">
<td colspan="2">
<asp:LinkButton ID="LinkButton4" runat="server" CommandName="Update" Text="Update" />
<asp:LinkButton ID="LinkButton5" runat="server" CommandName="Cancel" Text="Cancel" CausesValidation="false" />
</td>
</tr>
</EditItemTemplate>
<InsertItemTemplate>
<asp:DynamicEntity ID="DynamicEntity3" runat="server" Mode="Insert" />
<tr class="td">
<td colspan="2">
<asp:LinkButton ID="LinkButton6" runat="server" CommandName="Insert" Text="Insert" />
<asp:LinkButton ID="LinkButton7" runat="server" CommandName="Cancel" Text="Cancel" CausesValidation="false" />
</td>
</tr>
</InsertItemTemplate>
<FooterTemplate>
</table>
</FooterTemplate>
</asp:FormView>
<asp:EntityDataSource ID="DetailsDataSource" runat="server" EnableDelete="true" EnableInsert="true" EnableUpdate="true" />
<asp:QueryExtender ID="QueryExtender1" TargetControlID="DetailsDataSource" runat="server">
<asp:ControlFilterExpression ControlID="GridView1" />
</asp:QueryExtender>
</asp:Panel>
我在EditTemplate部分添加了一个btnCalculateTotalCosts按钮。
在后面的代码中，我创建了一个ItemCommand控件
protected void FormView1_ItemCommand(object sender, FormViewCommandEventArgs e)
{
if (e.CommandName == "Calculate")
{
FormViewRow row = FormView1.Row;
decimal itemCosts;
decimal additionalCosts;
TextBox itemsCostTextBox = (TextBox)row.FindControl("ItemCosts");
TextBox additionalCostsTextBox = (TextBox)row.FindControl("AdditionalCosts");
TextBox totalCostsTextBox = (TextBox)row.FindControl("TotalCosts");
Decimal.TryParse(itemsCostTextBox.Text, out itemCosts);
Decimal.TryParse(additionalCostsTextBox.Text, out additionalCosts);
totalCostsTextBox.Text = (itemCosts + additionalCosts).ToString();
}
但我不断收到'错误对象引用没有设置为对象的实例'。我已经读过你必须首先将字段绑定到FormView，所以我尝试创建以下
protected void FormView1_DataBind(object sender, EventArgs e)
{
if (FormView1.CurrentMode == FormViewMode.Edit)
{
TextBox itemsCostTextBox = (TextBox)FormView1.FindControl("ItemCosts");
TextBox additionalCostsTextBox = (TextBox)FormView1.FindControl("AdditionalCosts");
TextBox totalCostsTextBox = (TextBox)FormView1.FindControl("TotalCosts");
}
}
并将标记中的DataBind引用为OnDataBinding =“FormView1_DataBind”，但这也不起作用，我收到同样的错误。
我真的试图解决这个问题，并意识到FindControl并没有“看到”FormView中的字段，但我无法理解如何做到这一点。
非常感谢任何帮助 谢谢
答案 0 :(得分：0)
FindControl()收到您要查找的控件的ID。从您发布的ASPX代码我发现您没有看到您要使用ID设置DynamicControl的{{1}}属性。这个方法的调用：
FindControl()传递TextBox itemsCostTextBox = (TextBox)row.FindControl("ItemCosts");
属性值而不是DataField。将ID属性添加到您要查找的所有ID。
还要考虑DynamicControl不执行递归搜索，它只在控件的子节点之间查找具有指定FindControl()的控件。
答案 1 :(得分：0)
如果它可以帮助其他人：
protected void FormView1_ItemCommand(object sender, FormViewCommandEventArgs e)
{
if (e.CommandName == "Calculate")
{
// ...
//instead of this...
TextBox itemsCostTextBox = (TextBox)row.FindControl("ItemCosts");
//(no need to use row here, just use the reference to the FormView;
//also no need to add an ID to DynamicControl because it creates
//its own ID out of the field name and template control name)
//cast like this...
var itemsCostTextBox = (TextBox)FormView1.FindFieldTemplate("ItemCosts").TemplateControl.FindControl("txtTextBox1");
//txtTextBox1 is the name of the specific web UI control inside of
//the DynamicData *.ascx template that you want access to
}
}