UpdateLookup field by Powershell Script

Target
Set up the value of the lookup filed(named Relation)in the SharePoint list by PowerShell script,
Summary
This script is based on the SortOrder filed as a unique key to configure the Relation filed, before running the script, please make sure two following points correctly:

The value of SortOrder field cannot be empty.

操作ロジックの唯一のルーラーとしてSortOrderフィールドが使用されていることを確認します.論理は、Current ItemのSortOrderフィールド値に基づいて最後の文字を削除した後、親のSortOrder値になります.SortOrder値が1桁のみの場合、トップレベルとして表す、追加処理.次のようなケースがあります.
First Level: 1,2,3,4.... Second LeveL: 11,12... , 21, 22..... 41, 42.... Third Level: 111, 112..... 411, 412..... 421, 422... ....

3, Once we have completed this relation configuration. so we can run the powershell script to update
 Powershell Code:
 

Write-Host "PowerShell JScript Loading...."



$snapin = Get-PSSnapin | Where-Object {$_.Name -eq 'Microsoft.SharePoint.Powershell'}

 if ($snapin -eq $null) {

     Write-Host "Loading SharePoint Powershell Snapin..."

     Add-PSSnapin "Microsoft.SharePoint.Powershell"

 }



$siteUrl = "http://shndtpln0633:9200"    #Input the url of your country site.

$LeftNavListUrl = "lists/RelationList"        #Input the relative Url of the target List. 





#*****************User-Define Functions******************#



#update the Looupup Field value

Function UpdateFieldValue( $item, $value){

    try

    {

        $item["Relation"] = $value

        $item.Update()    

        

        Write-Host "the item($($item.Title)) was updated successfully" -f White

    }

    catch{

      write-host "Error, There an issue happened for updating the item($($item.Title))" -f red

    }

}



#Get Parent Value

Function GetParentValue($value){

    

    $result = $value

    if(([System.String]$value).length -cge 2){

    

        $result  = $value.substring(0, $value.length-1)

    }

    else{

        $result = "0"    

    }

    return $result

}



#Get the value from the parent item

Function GetLookupValue($List, $SortOrder){

    $res = ""

    try

    {

        $caml="<Where><Eq><FieldRef Name='SortOrder' /><Value Type='Number'>$SortOrder</Value></Eq></Where>"

        $query=new-object Microsoft.SharePoint.SPQuery

        $query.ViewAttributes = "Scope='Recursive'"

        $query.Query=$caml | Write-Output

        $items=$List.GetItems($query)        

        if ($items -cne $null){

            if($items.Count -cge  1){                            

                $res ="$($items[0].ID);#$($items[0].Title)"

            }

        }

    }

    catch

    {

        write-host "Error, there an error for getting Lookup value ." -f white

        write-host $Error[0] -f red

    }

    return $res

}

#*****************************************





#******************************************

#*********** Main Process******************

#******************************************



$site = Get-SPSite -Identity $siteUrl

$LeftNavList = $site.RootWeb.GetList($LeftNavListUrl)



foreach($item in $LeftNavList.Items){    

    if(($item.Title -ne "Top") -and ($item.Title -ne "Parent")) {    

        $sOrder = $item["SortOrder"].ToString()        

        if($sOrder -ne ""){        

        

            $pOrder =  GetParentValue $sOrder        

             $lookupParent = GetLookupValue $LeftNavList $pOrder

            if($lookupParent -ne ""){

                UpdateFieldValue $item $lookupParent 

            }

        }

        else{        

            write-host "The key(SortOrder field) has no value in the item $($item.Title), Please Check." -f red        

        }

        

    

    }

}

Write-Host "Operated Completedly!"

#Dispose of the site object

$site.Dispose()