VB.NET Requires Chilkat v11.7.0+
Box: Find a File by Name Across All Folder Pages

Run the reusable setup once per HttpCurl object, then select names and execute the operation. The setup is repeated here only to make this published example independently runnable. Find one exact, case-sensitive filename in a parent folder selected by name, checking the item type and every page before using its ID.
See the Box API guide for setup and the complete workflow.
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Dim success As Boolean = False

'  Requires Chilkat 11.7.0 or later and a previously unlocked Chilkat bundle.
'  See Global Unlock Sample.
'  Guide: Box API Guide.

success = False

'  BEGIN ONE-TIME SETUP
'  This block is repeated so each published example can run on its own.
'  In an application, run the setup example once and pass the SAME curl object
'  to operation code below. Do not recreate it for every operation.
'  See Reusable Box HttpCurl Setup.
Dim curl As New Chilkat.HttpCurl
curl.SetVar("access_token","BOX_ACCESS_TOKEN")
curl.SetVar("parent_name","/")
'  Box's fixed root ID is an implementation detail; callers supply names.
curl.SetVar("parent_id","0")
Dim setupCommand As New Chilkat.StringBuilder
Dim setupReplacements As Integer

'  Register findParent; registration sends no request.
setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("findParent",setupCommand.GetAsString())
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If


'  Register findFolder; registration sends no request.
setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/folders/{{parent_id}}/items?limit=1000&fields=id,type,name"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("findFolder",setupCommand.GetAsString())
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If


'  Register findFile; registration sends no request.
setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/folders/{{folder_id}}/items?limit=1000&fields=id,type,name"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("findFile",setupCommand.GetAsString())
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If


'  Register findDestination; registration sends no request.
setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/folders/0/items?limit=1000&fields=id,type,name"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("findDestination",setupCommand.GetAsString())
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If


'  Register getFileDetails; registration sends no request.
setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/files/{{file_id}}?fields=id,sha1,file_version"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("getFileDetails",setupCommand.GetAsString())
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If


'  Register getEnterprise; registration sends no request.
setupCommand.SetString("curl -X GET ""https://api.box.com/2.0/users/me?fields=enterprise"" -H ""Authorization: Bearer ACCESS_TOKEN""")
setupReplacements = setupCommand.Replace("ACCESS_TOKEN",curl.GetVar("access_token"))
success = curl.AddFunction("getEnterprise",setupCommand.GetAsString())
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If


'  Register output rules once. Chilkat 11.7.0 evaluates {{name}} variables
'  when extracting each output, using the current value at that time.
success = curl.AddOutput2("findParent","entries","name","{{parent_name}}",True,"id","parent_id")
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If

success = curl.AddOutput2("findFolder","entries","name","{{folder_name}}",True,"id","folder_id")
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If

success = curl.AddOutput2("findFile","entries","name","{{file_name}}",True,"id","file_id")
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If

success = curl.AddOutput2("findDestination","entries","name","{{destination_name}}",True,"id","destination_id")
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If

success = curl.AddOutput("getFileDetails","file_version.id","file_version_id")
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If

success = curl.AddOutput("getFileDetails","sha1","file_sha1")
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If

success = curl.AddOutput("getEnterprise","enterprise.id","enterprise_id")
If (success <> True) Then
    Debug.WriteLine(curl.LastErrorText)
    Exit Sub
End If

'  END ONE-TIME SETUP
'  The name lookups below assume each listing fits in one page (1000 items).
'  Parent and destination names select root children; folder_name selects a child
'  of parent_name. "/" selects the root parent. These are not arbitrary paths.

'  BEGIN OPERATION -- keep the configured object when reusing it.
'  Inputs are names. Retain cached IDs when the selected names have not changed.
Dim parentName As String = "/"
Dim folderName As String = "images"
If ((curl.GetVar("parent_name") <> parentName) Or ((parentName = "/") And (curl.VarDefined("parent_id") = False))) Then
    curl.SetVar("parent_name",parentName)
    curl.ClearVar("parent_id")
    curl.ClearVar("folder_id")
    curl.ClearVar("file_id")
    curl.ClearVar("file_version_id")
    curl.ClearVar("file_sha1")
    If (parentName = "/") Then
        curl.SetVar("parent_id","0")
    End If

End If

If (curl.GetVar("folder_name") <> folderName) Then
    curl.SetVar("folder_name",folderName)
    curl.ClearVar("folder_id")
    curl.ClearVar("file_id")
    curl.ClearVar("file_version_id")
    curl.ClearVar("file_sha1")
End If

curl.SetVar("marker","")
Dim page As New Chilkat.JsonObject
Dim i As Integer = 0
Dim count As Integer = 0
Dim more As Boolean = True
Dim nextMarker As String
Dim authorizedCommand1 As New Chilkat.StringBuilder
authorizedCommand1.SetString("curl -X GET ""https://api.box.com/2.0/folders/{{folder_id}}/items?usemarker=true&limit=1000&fields=id,type,name"" -H ""Authorization: Bearer {{access_token}}""")
Dim headerReplacement1 As Integer = authorizedCommand1.Replace("{{access_token}}",curl.GetVar("access_token"))
Dim pageCommand As String = authorizedCommand1.GetAsString()
Dim wantedName As String = "penguins.jpg"
Dim fileId As String = ""
Dim matches As Integer = 0
While (more = True)
    curl.ClearTargetOutput("*")
    success = curl.DoYourThing(pageCommand)
    If ((success <> True) Or (curl.StatusCode <> 200)) Then
        Debug.WriteLine("Box request failed. HTTP status: " & curl.StatusCode)
        Debug.WriteLine("Failure reason: " & curl.FailReason)
        Debug.WriteLine(curl.ResponseBodyStr)
        Exit Sub
    End If

    success = curl.GetResponseJson(page)
    If (success <> True) Then
        Debug.WriteLine(curl.LastErrorText)
        Exit Sub
    End If

    count = page.SizeOfArray("entries")
    i = 0
    While i < count
        page.I = i
        If ((page.StringOf("entries[i].type") = "file") And (page.StringOf("entries[i].name") = wantedName)) Then
            fileId = page.StringOf("entries[i].id")
            matches = matches + 1
        End If

        i = i + 1
    End While
    more = False
    If (page.HasMember("next_marker") = True) Then
        If (page.IsNullOf("next_marker") = False) Then
            nextMarker = page.StringOf("next_marker")
            If (nextMarker <> "") Then
                If (nextMarker = curl.GetVar("marker")) Then
                    Debug.WriteLine("Box returned the same pagination marker; stopping.")
                    Exit Sub
                End If

                curl.SetVar("marker",nextMarker)
                Dim authorizedCommand2 As New Chilkat.StringBuilder
                authorizedCommand2.SetString("curl -X GET ""https://api.box.com/2.0/folders/{{folder_id}}/items?usemarker=true&limit=1000&fields=id,type,name&marker={{marker}}"" -H ""Authorization: Bearer {{access_token}}""")
                Dim headerReplacement2 As Integer = authorizedCommand2.Replace("{{access_token}}",curl.GetVar("access_token"))
                pageCommand = authorizedCommand2.GetAsString()
                more = True
            End If

        End If

    End If

End While
If (matches <> 1) Then
    Debug.WriteLine("Expected exactly one matching file. Matches: " & matches)
    Exit Sub
End If

curl.SetVar("file_id",fileId)
Debug.WriteLine("File ID: " & fileId)
curl.ClearTargetOutput("*")
Dim authorizedCommand3 As New Chilkat.StringBuilder
authorizedCommand3.SetString("curl -X GET ""https://api.box.com/2.0/files/{{file_id}}?fields=id,type,name,parent,size"" -H ""Authorization: Bearer {{access_token}}""")
Dim headerReplacement3 As Integer = authorizedCommand3.Replace("{{access_token}}",curl.GetVar("access_token"))
success = curl.DoYourThing(authorizedCommand3.GetAsString())
If ((success <> True) Or (curl.StatusCode <> 200)) Then
    Debug.WriteLine("Box request failed. HTTP status: " & curl.StatusCode)
    Debug.WriteLine("Failure reason: " & curl.FailReason)
    Debug.WriteLine(curl.ResponseBodyStr)
    Exit Sub
End If

Debug.WriteLine(curl.ResponseBodyStr)