CODEWITHSUNDEEP
asp.netvb.net
Silentbob
Silentbob

Reputation: 3065

Finding and looping through labels

Running VS 2013 VB.net.

I have 3 labels on my aspx page labelled label1, label2 and label3.

I want to loop through each one in the code behind and assign values to them.

Here is my code

Dim X As Integer = 1

For Each obj In values

    Dim myLabel As Label
    myLabel = TryCast(Me.FindControl("Label" + X), Label)
    myLabel.Text = Math.Round(obj, 2)

    X = X + 1

Next

I know there is only 3 obj's so x will always be between 1 and 3. What am I doing wrong as I get the following.

Conversion from string "Label" to type 'Double' is not valid

IF I change ("label" + x) to ("label1") I get

Object reference not set to an instance of an object.

on the line below.

Upvotes: 1

Views: 585

Answers (2)

Tim Schmelter
Tim Schmelter

Reputation: 460228

You want to concatenate strings not to calculate, in VB.NET you use & instead of +(as opposed to C#). So this should work:

myLabel = TryCast(Me.FindControl("Label" & X), Label)

You should also set Option Strict to On, without exception. Then you first have to fix a lot of compiler errors, but it will help to write much more robust code. This wouldn't compile either:

myLabel.Text = Math.Round(obj, 2)

because a Math.Round returns a Double and Label.Text is a String. You just need to use Math.Round(obj, 2).ToString() to fix it.

Here's a different approach to get your labels using Linq:

Dim myLabels = From lbl In Me.Form.Controls.OfType(Of Label)()
               Where lbl.ID.StartsWith("Label")
For Each lbl As Label In myLabels
    ' ... '
Next

Upvotes: 2

OneFineDay
OneFineDay

Reputation: 9024

Also since your using TryCast check your variable before using it - it will be Nothing if it does not make the cast.

myLabel = TryCast(Me.FindControl("Label" & X.ToString), Label)
If myLabel IsNot Nothing Then
  'safe to use variable here
End If

Upvotes: 0

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