Question

I have checkbox control on gridview with the ability to check all and uncheck all.

The page also uses pagination. Each page has 25 records. Of course anymore more goes to the next page.

A user checks one or more checkboxes and user’s selections are processed using the code below:

Dim uItems As String = String.Empty 

For Each r As GridViewRow In GridView1.Rows 

    If CType(r.Cells(0).FindControl("recs"), CheckBox).Checked Then 

        If uItems <> String.Empty Then 

            uItems += "," 

        End If 

        uItems += "http://default.html?gen=" & r.Cells(1).Text & "&NO=3&F=1" 

    End If 

Next 

If a user checks 15 or less, then you get this:

http://default.html?gen=" & r.Cells(1).Text & "&NO=3&F=1 this works because you get as many as you checked.

The issue we are having currently is that if a user checks more than 15 checkboxes, we get

“Internet Explorer cannot display webpage; what you can try – diagnose connection…”

After several troubleshooting, we discovered that the reason it is breaking is we could pass more than 15 values from cell(1) to the that link.

Does anyone know of a workaround to this?

This was exactly the same problem I posted yesterday except that I was describing it incorrectly, thereby making it difficulty for experts to give the correct solution.

Thanks for your help.

Answer 1

I suspect that you are generating a query string that is too long but there are other issues with the code. I’ve changed it to use a StringBuilder and save repeated instantiation of Strings.

Dim uItems As New StringBuilder("http://default.html?gen=")

For Each r As GridViewRow In GridView1.Row
    If CType(r.Cells(0).FindControl("recs"), CheckBox).Checked Then
        uItems.AppendFormat("{0},", r.Cells(1).Text)
    End If
End For

-- Remove trailing delimiter
uItems.Remove(uItems.Length - 1, 1)

uItems.Append("&NO=3&F=1")

With this code uItems.ToString() will give you somthing like this

http://default.html?gen=bla1,bla2,bla3&NO=3&F=1

it may be that you actually want somthing like this.

Dim uItems As New StringBuilder("http://default.html?")

Dim checkCount = 0
For Each r As GridViewRow In GridView1.Row
    If CType(r.Cells(0).FindControl("recs"), CheckBox).Checked Then
        uItems.AppendFormat("g{0}={1}&", checkCount, r.Cells(1).Text)
        checkCount += 1
    End If
End For

-- Remove trailing delimiter
uItems.Remove(uItems.Length - 1, 1)

uItems.Append("&NO=3&F=1")

This will enumerate the checked cells in your query string and give you somthing like this.

http://default.html?g1=bla1&g2=bla2&g3=bla3&NO=3&F=1

---

To Return a URL for each checked Item

Dim urlItems = New List(Of String)()

Const urlFormat As String = _
    "http://default.html?gen={0}&NO=3&F=1"

For Each r As GridViewRow In GridView1.Row
    If CType(r.Cells(0).FindControl("recs"), CheckBox).Checked Then
        Dim url = String.Format(urlFormat, r.Cells(1).Text)
        urlItems.Add(url)
    End If
End For

This makes urlItems that is a generic List of Strings, each item being a url

---

Okay the bit above shows you how to get a list of url Strings so, to iterate the urls do

For Each url As String In urlItems
    //... Some code for POSTing or GETting .. your request 
End For