<div>
You could put it in the change event to change the other, and use an If statement: (psuedocode below) 
 
if (combox1 == combox2) 
{ 
// do nothing 
} 
 
else 
{ 
combox2 = combox1 
}
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<div>
I still get an infinte loop, 
 
code in form1 

<pre><code class="code-10 nolinks" id="code-8225822">Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 Form2.Show()
 End Sub

 Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
 If Form2.ComboBox1.SelectedIndex = Me.ComboBox1.SelectedIndex Then
 Console.WriteLine(&quot;same1&quot;)
 Else
 Form2.ComboBox1.SelectedIndex = Me.ComboBox1.SelectedIndex
 End If
 End Sub
</code></pre>
 
code in form2 
&nbsp;
<pre><code class="code-1 nolinks" id="code-8225824">If Form1.ComboBox1.SelectedIndex = Me.ComboBox1.SelectedIndex Then
 Console.WriteLine(&quot;same2&quot;)
 Else
 Form1.ComboBox1.SelectedIndex = Me.ComboBox1.SelectedIndex
 End If
</code></pre>
</div>

<div>
Hi CodeCruiser, 
 
I get the following error if I have items in the combobox at design time. &nbsp; 
If I clear out the items and add them at run time, the code works. 
 
 
System.InvalidOperationException was unhandled 
&nbsp; Message=An error occurred creating the form. See Exception.InnerException for details. &nbsp;The error is: InvalidArgument=Value of '0' is not valid for 'SelectedIndex'. 
Parameter name: SelectedIndex 
... 
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<div>
Hi CodeCruiser, 
 
I have the combobox in 2 separate forms and I was able to get the following code to work based on your method.. &nbsp;Any &nbsp;other suggestions? 
 

<pre><code class="code-10 nolinks" id="code-8225828">Public Class Form1
 Public IsSynchingA, IsSynchingB As Boolean
 Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
 If Not IsSynchingB Then
 IsSynchingA = True
 Form2.ComboBox1.SelectedIndex = Me.ComboBox1.SelectedIndex
 IsSynchingA = False
 MsgBox(&quot;CB1&quot;)
 End If
 End Sub

 Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 Form2.Show()
 Me.ComboBox1.Items.Clear()
 Form2.ComboBox1.Items.Clear()
 For i As Integer = 1 To 5
 Me.ComboBox1.Items.Add(i)
 Form2.ComboBox1.Items.Add(i)
 Next
 Me.ComboBox1.SelectedIndex = 0
 End Sub
End Class

Public Class Form2
 Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
 If Not Form1.IsSynchingA Then
 Form1.IsSynchingB = True
 Form1.ComboBox1.SelectedIndex = Me.ComboBox1.SelectedIndex
 Form1.IsSynchingB = False
 MsgBox(&quot;CB2&quot;)
 End If
 End Sub
End Class
</code></pre>
</div>

<div>
Do you mean you are unable to get this to work? 
 
Does it work if you comment out the below line? 
 
Me.ComboBox1.SelectedIndex = 0
</div>

<div>
It works, but only if the comboboxes are blank on startup.
</div>

<div>
<div class="content wysiwyg-content">
I have a combo box in 2 separate forms. &nbsp;I want both to be in sync bidirectionally - a change in one updates the other. How can I do that without resulting in an infinite loop? &nbsp;I'm using VB.net. &nbsp;Thanks. 
</div>
</div>

I have a combo box in 2 separate forms.  I want both to be in sync bidirectionally - a change in one updates the other. How can I do that without resulting in an infinite loop?  I'm using VB.net.  Thanks. 

syncing combo box selected item

Visual Basic .NET (VB.NET) is an object-oriented programming language implemented on the .NET framework, but also supported on other platforms such as Mono and Silverlight. Microsoft launched VB.NET as the successor to the Visual Basic language. Though it is similar in syntax to  Visual Basic pre-2002, it is not the same technology,