Exchange with Powershell - weird error

I enter my code and it throws an error. The code went fine and I was able to run it before I tried to add the Dropbox feature. I can't seem to figure out what is wrong with this ...

Method invocation failed because [System.Reflection.RuntimeAssembly] does not contain a method named 'op_A
At C:\scripts\tmail1.ps1:127 char:1
+ $return2 = ($return[0] + " " + $return[1])
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (op_Addition:String) [], RuntimeException
    + FullyQualifiedErrorId : MethodNotFound

Method invocation failed because [System.Reflection.RuntimeAssembly] does not contain a method named 'op_A
At C:\scripts\tmail1.ps1:128 char:1
+ $return3 = ($return[0] + "." + $return[1])
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (op_Addition:String) [], RuntimeException
    + FullyQualifiedErrorId : MethodNotFound

Method invocation failed because [System.Reflection.RuntimeAssembly] does not contain a method named 'op_A
At C:\scripts\tmail1.ps1:129 char:1
+ $return4 = $return[0] + "." + $return[1] + $return[2]
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (op_Addition:String) [], RuntimeException
    + FullyQualifiedErrorId : MethodNotFound

Cannot validate argument on parameter 'Alias'. The argument is null or empty. Provide an argument that is
empty, and then try the command again.
    + CategoryInfo          : InvalidData: (:) [New-Mailbox], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,New-Mailbox
    + PSComputerName        : pqhiexch01.xxxxxxx.com

Cannot bind argument to parameter 'Identity' because it is null.
    + CategoryInfo          : InvalidData: (:) [Set-User], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Set-User

      

        
        
        
      

    

My code looks like this:

function button ($title,$mailbx, $WF, $TF) {

###################Load Assembly for creating form & button######

[void][System.Reflection.Assembly]::LoadWithPartialName( "System.Windows.Forms")
[void][System.Reflection.Assembly]::LoadWithPartialName( "Microsoft.VisualBasic")

#####Define the form size & placement

$form = New-Object "System.Windows.Forms.Form";
$form.Width = 750;
$form.Height = 500;
$form.Text = $title;
$form.StartPosition = [System.Windows.Forms.FormStartPosition]::CenterScreen;

##############Define text label1
$textLabel1 = New-Object "System.Windows.Forms.Label";
$textLabel1.Left = 25;
$textLabel1.Top = 15;

$textLabel1.Text = $mailbx;

##############Define text label2

$textLabel2 = New-Object "System.Windows.Forms.Label";
$textLabel2.Left = 25;
$textLabel2.Top = 50;

$textLabel2.Text = $WF;

##############Define text label3

########################

# Edit This item to change the DropDown Values

[array]$DropDownArray = "@yahoo.com", "@gmail.com", "@msn.com"

$textLabel3 = New-Object "System.Windows.Forms.Label";
$textLabel3.Left = 25;
$textLabel3.Top = 85;

$textLabel3.Text = $TF;

############Define text box1 for input
$textBox1 = New-Object "System.Windows.Forms.TextBox";
$textBox1.Left = 150;
$textBox1.Top = 10;
$textBox1.width = 200;

############Define text box2 for input

$textBox2 = New-Object "System.Windows.Forms.TextBox";
$textBox2.Left = 150;
$textBox2.Top = 50;
$textBox2.width = 200;

############Define text box3 for input

# This Function Returns the Selected Value and Closes the Form

function Return-DropDown {

 $Choice = $DropDown.SelectedItem.ToString()
 }

[System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")
[System.Reflection.Assembly]::LoadWithPartialName("System.Drawing")




$DropDown = new-object System.Windows.Forms.ComboBox
$DropDown.Location = new-object System.Drawing.Size(150,90)
$DropDown.Size = new-object System.Drawing.Size(200,30)

ForEach ($Item in $DropDownArray) {
 $DropDown.Items.Add($Item)
}

$Form.Controls.Add($DropDown)

$DropDownLabel = new-object System.Windows.Forms.Label
$DropDownLabel.Location = new-object System.Drawing.Size(150,90) 
$DropDownLabel.size = new-object System.Drawing.Size(100,20) 
$DropDownLabel.Text = "Items"
#############Define default values for the input boxes
$defaultValue = ""
$textBox1.Text = $defaultValue;
$textBox2.Text = $defaultValue;


#############define OK button
$button = New-Object "System.Windows.Forms.Button";
$button.Left = 360;
$button.Top = 85;
$button.Width = 100;
$button.Text = "Ok";

############# This is when you have to close the form after getting values
$eventHandler = [System.EventHandler]{
$textBox1.Text;
$textBox2.Text;
$dropdown.Items;
$form.Close();};

$button.Add_Click($eventHandler) ;

#############Add controls to all the above objects defined
$form.Controls.Add($button);
$form.Controls.Add($textLabel1);
$form.Controls.Add($textLabel2);
$form.Controls.Add($textLabel3);
$form.Controls.Add($textBox1);
$form.Controls.Add($textBox2);
$Form.Controls.Add($DropDownLabel)
$Button.Add_Click({Return-DropDown});
$ret = $form.ShowDialog();

#################return values

return $textBox1.Text, $textBox2.Text, $textBox3.Text
}

$return= button "Enter Info" "First Name" "Last Name" "Email Address"
$return2 = ($return[0] + " " + $return[1])
$return3 = ($return[0] + "." + $return[1])
$return4 = $return[0] + "." + $return[1] + $return[2]


New-Mailbox -Alias $return3 -Name $return2 -FirstName $return[0] -LastName $return[1] -UserPrincipalName $return4  -Password (ConvertTo-SecureString -String 'P@ssw0rd' -AsPlainText -Force) -ResetPasswordOnNextLogon $true
Set-User -Identity $return3 -StreetAddress '1600 Pennsylvania Ave NW' -City 'Washington' -StateOrProvince 'D.C.' -PostalCode '20500' -Phone '202-456-1111' -Fax '202-456-2461'