<apex:page controller="CreateMulItem" sidebar="false" >
<apex:form >
<apex:pageBlock >
<apex:pageBlockButtons >
<apex:commandButton value="Save Task" action="{!Save}" />
</apex:pageBlockButtons>

<apex:commandButton value="Save" action="{!Save}" />
</apex:pageBlockButtons> -->
<apex:pageBlockSection title="Create Items" >

<apex:outputLabel Value="Item Name" style="margin-left:10%;position:relative;top:10px;font-weight:bold" >
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;
<apex:selectList value="{!ItemTemp}" size="1" >

<apex:selectOptions value="{!Itemname}"/>

</apex:selectList>
</apex:outputLabel>

</apex:pageBlockSection>



<apex:outputlabel value="Create New Item" for="newval" style="margin-left:4%;position:relative;top:20px;font-weight:bold" />
<apex:inputText value="{!newpicklistvalue}" id="newval" style="margin-left:4%;position:relative;top:15px;font-weight:bold" />
<apex:commandbutton action="{!saverec}" value="Add Item!" style="margin-left:4%;position:relative;top:15px;font-weight:bold" />



<apex:pageBlockSection title="Add parent and child Item">
<apex:outputLabel Value="Parent Items" style="margin-left:10%;position:relative;top:10px;font-weight:bold" >
<apex:selectList value="{!ParentTemp}" size="3" multiselect="true" >
<apex:selectOptions value="{!ParentItem}"/>
</apex:selectList>
</apex:outputLabel>

<apex:outputLabel Value="Child Items " style="margin-Right:1%;position:relative;top:10px;font-weight:bold" >
<apex:selectList value="{!ChildTemp}" size="3" multiselect="true" >
<apex:selectOptions value="{!ChildItem}"/>
</apex:selectList>
</apex:outputLabel>
</apex:pageBlockSection>

</apex:pageBlock>

</apex:form>
</apex:page>

class:

public with sharing class CreateMulItem{

// Declare variables

public String ParentTemp { get; set; }
public String ChildTemp { get; set; }
public String ItemTemp{get; set;}

// Load Parent Items
public List<SelectOption> getParentItem() {
List<SelectOption> options = new List<SelectOption>();

for(Item_relation__c Itemrelation :[Select id,Name,parent_item__c,child_item__c from Item_relation__c ]){
options.add(new SelectOption(Itemrelation.id,Itemrelation.name));
}
return options;
}

// Load Child Items
public List<SelectOption> getChildItem() {
List<SelectOption> options = new List<SelectOption>();
// options.add(new SelectOption('--None--','--None--'));
for(Item_relation__c Itemrelation :[Select id,Name,parent_item__c,child_item__c from Item_relation__c ]){
options.add(new SelectOption(Itemrelation.id,Itemrelation.Name));
}
return options;
}
// Load Child Items
public List<SelectOption> getItemname() {
List<SelectOption> options = new List<SelectOption>();
// options.add(new SelectOption('--None--','--None--'));
for(Item_relation__c Itemrelation :[Select id,Name,parent_item__c,child_item__c from Item_relation__c where Name != 'None' ]){
options.add(new SelectOption(Itemrelation.id,Itemrelation.Name));
}
return options;
}
public String newpicklistvalue{get; set;}

public void saverec()
{
Item_relation__c newrec = new Item_relation__c(name = newpicklistvalue);

insert newrec;
newpicklistvalue=NULL;
}

// Save Item Relations
public List<Item_relation__c> saverelations {get; set;}

public PageReference Save() {

Item_relation__c Sitems = new Item_relation__c();

Sitems =[select id,name, parent_item__c,child_item__c from Item_relation__c where id =: ItemTemp];


Sitems.parent_item__c = ParentTemp;
Sitems.child_item__c = ChildTemp;
update Sitems;

PageReference parrec = new PageReference('https://ap1.salesforce.com/a0A/o');
parrec.setRedirect(true);
return parrec;
}

}