为什么Web窗体上的复选框对Control循环代码不可见? [英] Why are the checkboxes on my Webform invisible to the Control loop code?

问题描述

注意:这与以前的问题有关此处和

NOTE: This is related to previous questions here and here, but I think I've narrowed it down to a clearer understanding of what the problem is.

我已经向Webforms应用程序手动添加了一个Checkbox，并动态生成了更多内容.

I have manually added a Checkbox to a Webforms app, and dynamically generate a bunch more.

我想遍历这些复选框，并有条件地执行具有相关值的操作，但是该循环根本找不到任何复选框，甚至在设计时都没有从工具箱拖放到Webform上的复选框.这是寻找复选框的代码:

I want to loop over these Checkboxes, and conditionally do something with a related value, but the loop finds no Checkboxes at all, not even the one that was dropped on the Webform from the Toolbox at design time. This is the code that looks for the checkboxes:

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim connStr As String = "SERVER=dishwasher;DATABASE=restaurant;UID=jack;PWD=london"
    Dim upd8DML As String = "UPDATE CustomerCategoryLog SET Category = 'Exploding' WHERE Unit = @Unit And MemberNo = @MemberNo AND Custno = @CustNo"

    Dim coName As String
    Dim argVals(2) As String
    Dim _Unit As String
    Dim _MemberNo As String
    Dim _CustNo As String
    Dim curCheckboxIDVal As String
    Label2.Text = "label 2 text from button1_click"
    LabelDebug.Text = "label debug text from button1_click"

    For Each cntrl As Control In Me.Controls
        Label2.Text = "label 2 text from foreach"
        LabelDebug.Text = LabelDebug.Text + " " + cntrl.GetType().ToString + " "
        'If TypeOf cntrl Is System.Web.UI.WebControls.CheckBox Then
        If String.IsNullOrEmpty(cntrl.ID) then Continue For
        If cntrl.ID.ToString().Contains("ckbx") Then
            Label2.Text = "label 2 text from is checkbox"
            If DirectCast(cntrl, CheckBox).Checked = True Then
                Label2.Text = "label 2 text from checked"
                curCheckboxIDVal = CStr(DirectCast(cntrl, CheckBox).ID)
                coName = GetLabelTextForID(curCheckboxIDVal)
                argVals = GetArgValsForCompanyName(coName)
                _Unit = argVals(0)
                _MemberNo = argVals(1)
                _CustNo = argVals(2)
                Label2.Text = _Unit
                LabelDebug.Text = _MemberNo
                Using conn As New SqlConnection(connStr), _
                    cmd As New SqlCommand(upd8DML, conn)
                    cmd.Parameters.Add("@Unit", SqlDbType.VarChar, 50).Value = _Unit
                    cmd.Parameters.Add("@MemberNo", SqlDbType.VarChar, 50).Value = _MemberNo
                    cmd.Parameters.Add("@CustNo", SqlDbType.VarChar, 50).Value = _CustNo
                    conn.Open()
                    cmd.ExecuteScalar()
                End Using
            End If
        End If
    Next
End Sub

请注意，我正在尝试查找ID包含"ckbx"的任何控件，因为搜索Checkbox类型的控件失败.但这也莫名其妙地失败了.

Note that I am trying to find any control with an ID that contains "ckbx", since searching for those of type Checkbox failed. But that inexplicably fails, too.

这是我在合并运行上面代码的按钮之前在页面上看到的(如您所见，有多个复选框，其中大多数是页面上在Page_Init期间动态生成的):

This is what I see on the page just prior to mashing the button that runs the code above (as you can see, there are several checkboxes, most of which are dynamically generated during Page_Init, on the page):

通过在粘贴按钮之前选择查看源代码"(这将遍历表单的Control集合)，我看到了:

By selecting "View Source" just prior to mashing the button (which will loop over the form's Control collection), I see this:

    <input id="CheckBox1" type="checkbox" name="CheckBox1" />
    <p>
        <span id="LabelDebug">label debug text from page_load</span>
    </p>
<span id="lbl0"> AMC THEATRES - TYSON CORNER 16</span><input id="ckbx0" type="checkbox" name="ckbx0" checked="checked" /><span><br></span><span id="lbl1"> GSO AIRPORT - ACC</span><input id="ckbx1" type="checkbox" name="ckbx1" checked="checked" /><span><br></span><span id="lbl2"> LONGHORN - DES PLAINS</span><input id="ckbx2" type="checkbox" name="ckbx2" checked="checked" /><span><br></span><span id="lbl3"> MAGGIE'S </span><input id="ckbx3" type="checkbox" name="ckbx3" checked="checked" /><span><br></span><span id="lbl4"> OAKRIDGE NURSING & REHAB NO LGER FB 11296</span><input id="ckbx4" type="checkbox" name="ckbx4" checked="checked" /><span><br></span><span id="lbl5"> SKYPORT - WOODY CREEK B&C DIA C-C </span><input id="ckbx5" type="checkbox" name="ckbx5" checked="checked" /><span><br></span><span id="lbl6"> UNIV NORTH CAROLINA - CHARLOTTE - BAKERY #32936</span><input id="ckbx6" type="checkbox" name="ckbx6" checked="checked" /><span><br></span><span id="lbl7">"DRAKE ""SIMPLY TO GO/OLMSTED #2"</span><input id="ckbx7" type="checkbox" name="ckbx7" checked="checked" /><span><br></span><span id="lbl8">"DRAKE CENTER   SCS""OLD ACCOUNT"""</span><input id="ckbx8" type="checkbox" name="ckbx8" checked="checked" /><span><br></span><span id="lbl9">"HUT, THE - EMORY & HENRY"</span><input id="ckbx9" type="checkbox" name="ckbx9" checked="checked" /><span><br></span><span id="lbl10">"THOMAS MORE COLLEGE   SCS ""OLD"""</span><input id="ckbx10" type="checkbox" name="ckbx10" checked="checked" /><span><br></span><span id="lbl11">"WRIGHT STATE ""C"" STORE  SCS"</span><input id="ckbx11" type="checkbox" name="ckbx11" checked="checked" /><span><br></span></form>

所有复选框都在那里并占了-为什么循环对它们不可见?

So all the checkboxes are there and accounted for - so why is the loop blind to them?

页面中是否可能存在其他阻碍成功的事情?如果是这样，也许可以从整个(Web)工具包&来自查看源代码"的kaboodle:

Is there possibly something else in the page that is preventing success here? If so, maybe it is discernible from the whole (web)kit & kaboodle from the "View Source":

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>
    Customer Category Maintenance
</title></head>
<body>
    <form name="formCustCatMaint" method="post" action="custmaint_categoryadmin.aspx" id="formCustCatMaint">
<div>
<input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUKLTE1Mzg3MzEyNA9kFgICAw9kFgQCBQ8PFgIeBFRleHQFG2xhYmVsIDIgdGV4dCBmcm9tIHBhZ2VfbG9hZGRkAgkPDxYCHwAFH2xhYmVsIGRlYnVnIHRleHQgZnJvbSBwYWdlX2xvYWRkZBgBBR5fX0NvbnRyb2xzUmVxdWlyZVBvc3RCYWNrS2V5X18WDQUJQ2hlY2tCb3gxBQVja2J4MAUFY2tieDEFBWNrYngyBQVja2J4MwUFY2tieDQFBWNrYng1BQVja2J4NgUFY2tieDcFBWNrYng4BQVja2J4OQUGY2tieDEwBQZja2J4MTEOVoGeHarmK0RaIVFgiYF1MfX7+A==" />
</div>

<div>

    <input type="hidden" name="__VIEWSTATEGENERATOR" id="__VIEWSTATEGENERATOR" value="2AC5B239" />
    <input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="/wEWDwL10YNmAoznisYGAoLk17sJAsO3wKgLAsS3wKgLAsG3wKgLAsK3wKgLAse3wKgLAsi3wKgLAsW3wKgLAsa3wKgLAru3wKgLAry3wKgLAsS3gKgLAsS3/KcLI6zphO0y3z+gPnFXloHFrZsHghg=" />
</div>
        <input type="submit" name="Button1" value="Update checked from &quot;New&quot; to &quot;Existing&quot; (uncheck any that should remain &quot;New&quot;)" id="Button1" style="width:612px;" />
        <span id="Label1"><br></span>
        <span id="Label2">label 2 text from page_load</span>
        <input id="CheckBox1" type="checkbox" name="CheckBox1" />
        <p>
            <span id="LabelDebug">label debug text from page_load</span>
        </p>
    <span id="lbl0"> AMC THEATRES - TYSON CORNER 16</span><input id="ckbx0" type="checkbox" name="ckbx0" checked="checked" /><span><br></span><span id="lbl1"> GSO AIRPORT - ACC</span><input id="ckbx1" type="checkbox" name="ckbx1" checked="checked" /><span><br></span><span id="lbl2"> LONGHORN - DES PLAINS</span><input id="ckbx2" type="checkbox" name="ckbx2" checked="checked" /><span><br></span><span id="lbl3"> MAGGIE'S </span><input id="ckbx3" type="checkbox" name="ckbx3" checked="checked" /><span><br></span><span id="lbl4"> OAKRIDGE NURSING & REHAB NO LGER FB 11296</span><input id="ckbx4" type="checkbox" name="ckbx4" checked="checked" /><span><br></span><span id="lbl5"> SKYPORT - WOODY CREEK B&C DIA C-C </span><input id="ckbx5" type="checkbox" name="ckbx5" checked="checked" /><span><br></span><span id="lbl6"> UNIV NORTH CAROLINA - CHARLOTTE - BAKERY #32936</span><input id="ckbx6" type="checkbox" name="ckbx6" checked="checked" /><span><br></span><span id="lbl7">"DRAKE ""SIMPLY TO GO/OLMSTED #2"</span><input id="ckbx7" type="checkbox" name="ckbx7" checked="checked" /><span><br></span><span id="lbl8">"DRAKE CENTER   SCS""OLD ACCOUNT"""</span><input id="ckbx8" type="checkbox" name="ckbx8" checked="checked" /><span><br></span><span id="lbl9">"HUT, THE - EMORY & HENRY"</span><input id="ckbx9" type="checkbox" name="ckbx9" checked="checked" /><span><br></span><span id="lbl10">"THOMAS MORE COLLEGE   SCS ""OLD"""</span><input id="ckbx10" type="checkbox" name="ckbx10" checked="checked" /><span><br></span><span id="lbl11">"WRIGHT STATE ""C"" STORE  SCS"</span><input id="ckbx11" type="checkbox" name="ckbx11" checked="checked" /><span><br></span></form>
</body>
</html>

推荐答案

此修正在事后看来很简单，甚至合乎逻辑.

The fix ended up being simple, and even logical, in hindsight.

将控件动态添加到表单中，如下所示:

The controls are dynamically added to the form, like so:

formCustCatMaint.Controls.Add(coName)

因此，在循环中替换此行:

And so, replacing this line, in the loop:

For Each cntrl As Control In Me.Controls

...与此:

For Each cntrl As Control In formCustCatMaint.Controls

这行，在GetLabelTextForID()函数中:

And this line, in the GetLabelTextForID() function:

For Each cntrl As Control In Me.Controls

...与此:

For Each cntrl As Control In formCustCatMaint.Controls

...成功了.找到控件，并且代码按设计/最初的预期运行.

...did the trick. The controls are being found, and the code is working as designed/originally expected.

Nebenbei bemerkt，现在也可以正常使用

Nebenbei bemerkt, this also works fine now:

If TypeOf cntrl Is CheckBox Then

这篇关于为什么Web窗体上的复选框对Control循环代码不可见?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！