dynamically set control ID

i have few texboxt and dropdownlist, which their id would be som开发者_开发知识库ething like "txtName1, txtName2, txtName3..." and "ddlAction1, ddlAction2, ddlAction3...."! I would to to dynamically set the textboxt and dropdownlist id into something like this:

for i as integer = 0 to 6
   a = txtName+i.text
   b = ddlAction+i.SelectedValue
next i

Need help from you guys to do this! thanks....

The key is FindControl, which looks up a control by its expected ID:

For i As Integer = 0 To 5
    Dim txt As TextBox = TryCast(Me.Page.FindControl("txtName" & i.ToString()), TextBox)
    Dim ddl As DropDownList = TryCast(Me.Page.FindControl("ddlAction" & i.ToString()), DropDownList)

    If txt IsNot Nothing AndAlso ddl IsNot Nothing Then
        Dim a As String = txt.Text
        Dim b As String = ddl.SelectedValue
    End If
Next

It will return null/nothing if a control with that ID isn't found.

Note that FindControl will only search the given control's (or Page's) immediate children, not the entire control tree. To search recursively, you need to use your own FindControl method.

Private Function FindControlRecursive(ByVal control As Control, ByVal id As String) As Control
    Dim returnControl As Control = control.FindControl(id)
    If returnControl Is Nothing Then
        For Each child As Control In control.Controls
            returnControl = child.FindControlRecursive(id)
            If returnControl IsNot Nothing AndAlso returnControl.ID = id Then
                Return returnControl
            End If
        Next
    End If
    Return returnControl
End Function

.Net requires you to resolve your variable names at compile time, rather than runtime like your code is trying to do. This is a good thing, as it prevents you from making certain kinds of errors. But it does mean you'll need to look at an alternative approach for this particular problem.

One option is a FindControl -based method. But odds are the controls you care about are grouped together on the page. If they aren't already, put them in a common container control, like a panel. Then you can do something like this (requires System.Linq):

For Each t As TextBox In MyContainer.Controls.OfType(Of TextBox)()
    a = t.Text
Next t

For Each d As DropDownList In MyContainer.Controls.OfType(Of DropDownList)()
    b = d.SelectedValue
Next d

Also, I hope you're really doing something other than assignment inside your loop. Otherwise, most of the work is for nothing as you will exit the loop having simply assigned the value from the last iteration to your variable.

Finally, it seems like these controls might work in pairs. To me, that's a situation that calls out for you to implement a user control.

I'm not a webforms expert, but I believe the page stores a reference to each control present in the page.

You can think of webforms like an n-ary tree... each control has a parent and can have 0 to many children. So, if these are static controls you should just be able to grab a reference to their parent and iterate over that... with no need for the children's ids.

Also, you can query for children based on their id... something like myControl["myID1"] so you can concat the number with the string and get the control that way.

Lastly, if these are purely dynamic controls, i.e. you don't know how many there are, just store references to them in an ordered collection and iterate over them that way.

EDIT:

Here we go:

WebControl myControl;
myControl.Controls.Add(someControlReference);

Then, to grab a control by ID:

WebControl someControl = myControl.FindControl("someControlID1");

From there you can do like:

string a = someControl.Text