split string (Ignore case sensitivity)

Here is my code

Dim AppNumber as string
           Dim arrCourse() As String 
       
arrCourse = Split(url, "app_")  // Now this is only splitting "app_" How Can I make it work for "APP_" as well (Need to ignore the case sensitivity"? 
 
 
      If arrCourse(1).IndexOf("/") > 0 Then
 
           AppNumber = arrCourse(1).Substring(0, arrCourse(1).IndexOf("/"))
 
        Else
           AppNumber = arrCourse(1)
 
        End If
I don't want to use
Regex.Split(url, "app_", RegexOptions.IgnoreCase)
Is there any other way of doing it??
 
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