Reading Environment Variables & Setting Control Values

[vbfailure]

Hello,

I'm looking for an opinion on a piece of code I've thrown together from a few examples I found on this site and elsewhere.

I've got an old program that I inherited at work (not really my job, I have next to zero programming ability but I have just have to do it), for whatever reason the author of this old program chose to keep the various configuration values for it in environment variables and there are a lot of them... 70+. Now I can't imagine this was a good idea even back in 1996 but here we are with no source code for the old software and a need to configure it without quite as much pain moving forward.

I wanted to avoid copy pasting a lot of code to read each environment variable so this is what I put together:

Dim EV As System.Collections.DictionaryEntry
 
        For Each EV In Environment.GetEnvironmentVariables()
 
            If EV.Key.ToString.StartsWith("LOBAppPrefix_") Then
 
                Dim ctl As Control = Me.GetNextControl(Me, True) 'Get the first control in the tab order.
 
                Do Until ctl Is Nothing
                    'Use ctl here.
 
                    If ctl.Name = EV.Key.ToString Then
 
                        If TypeOf ctl Is CheckBox Then
                            CType(ctl, CheckBox).Checked = True
                        ElseIf TypeOf ctl Is ComboBox Then
                            CType(ctl, ComboBox).SelectedValue = EV.Value.ToString
                        End If
 
                    End If
 
                    ctl = Me.GetNextControl(ctl, True) 'Get the next control in the tab order.
 
                Loop
 
            End If
 
        Next

I name the controls to match the environment variable and it does work how I expected but I would be interested to know if there is a better way of doing this that might improve its performance.

Thanks to jmcilhinney for a much easier to understand method of looping though all controls and pradeep for GetEnvironmentVariables example.

[si_the_geek]

Welcome to VBForums

Your code seems valid, just a bit long-winded and a bit inefficient (as it goes thru each control once for each LOBAppPrefix_ environment variable).

As you have the control names the same as the environment variables, you can actually get the controls by name. eg:

Dim EV As System.Collections.DictionaryEntry
 
        For Each EV In Environment.GetEnvironmentVariables()
 
            Dim EVKey as String = EV.Key.ToString
            If EVKey.StartsWith("LOBAppPrefix_") Then
 
                Dim ctl As Control = Me.Controls(EVKey)
                If TypeOf ctl Is CheckBox Then
                    CType(ctl, CheckBox).Checked = True
                ElseIf TypeOf ctl Is ComboBox Then
                    CType(ctl, ComboBox).SelectedValue = EV.Value.ToString
                End If
            End If
 
        Next

As for the original use of environment variables, it probably started out as just a few (and using environment variables for a few would have been sensible back then), and then expanded over time... at which point it wasn't such a great idea any more, but changing the code could have taken more time than it was worth.

[vbfailure]

Welcome to VBForums
Your code seems valid, just a bit long-winded and a bit inefficient (as it goes thru each control once for each LOBAppPrefix_ environment variable).

Thanks

That was the concern I had but I could not think of/find another way to do it aside from individually getting each environment variable and setting the control, I did briefly test doing that but when I put a timer on it to see what the performance was like it was quite slow.

As you have the control names the same as the environment variables, you can actually get the controls by name. eg:

I don't have my old code but I think I had something very close to that at one point but in trying to organize the form a little I have ended up with the controls are spread over 4 tabs. This lead me to finding the code from jmcilhinney, using it meant I did not have to worry about where the control was.

Thanks again!

[vbfailure]

I made a small change, it seems to have solved my problem with controls being in tabs. Is this any better than just looping through the controls like I was doing?

From:

Dim ctl As Control = Me.Controls(EVKey)

To:

Dim ctl As Control = Me.Controls.Find(EVKey, True)(0)

[si_the_geek]

In terms of speed it might be, I'm not sure so you'd need to test. It does make for simpler code tho, which is a nice thing to have.

An alternative is to invert the loops, so you find the controls, and then get the matching environment variable. eg:

Dim EnvironmentVariables As IDictionary = Environment.GetEnvironmentVariables()
        Dim ctl As Control = Me.GetNextControl(Me, True) 'Get the first control in the tab order.
        Do Until ctl Is Nothing
            If ctl.Name.StartsWith("LOBAppPrefix_") Then
                Dim EV As System.Collections.DictionaryEntry = EnvironmentVariables.Item(ctl.Name)
                If EV IsNot Nothing Then
 
                    If TypeOf ctl Is CheckBox Then
                        CType(ctl, CheckBox).Checked = True
                    ElseIf TypeOf ctl Is ComboBox Then
                        CType(ctl, ComboBox).SelectedValue = EV.Value.ToString
                    End If
 
                End If
                ctl = Me.GetNextControl(ctl, True) 'Get the next control in the tab order.
            End If
        Loop

This is untested, so may need minor fixes.. but it should be quick, as well as being simpler code (because one of the loops is replaced by a dictionary search).