Hi Team,

How can we update child record information from vf page and need to add pagination
controller :

public with sharing class DiplayRelatedContacts {
   public List<Account> accList{get;set;}
   public list<Contact> conList{get;set;}
   public String accId{get;set;}
   public DiplayRelatedContacts(){
       accList=[SELECT Id,Name,AccountNumber FROM Account LIMIT 10];
   
   }
    public PageReference dispalyContact() {
       if(accId != null)
        conList=[SELECT id,FirstName,LastName,Phone,Department,Birthdate FROM COntact WHERE AccountId=:accId];
        update conList;
        return null;
    }    

     public pagereference save() {
     	update accList;
     	update conList;
     	return null;
	}   
}

Vf page 
 

<apex:page controller="DiplayRelatedContacts" id="pg" lightningStylesheets="true">
    <apex:form id="frm">
        <apex:pageBlock id="pgblk" >
            <apex:pageBlockTable value="{!accList}" var="ac">
                <apex:column width="10px">
                    <input type="radio" name="group1" />
                    <apex:actionSupport event="onclick" action="{!dispalyContact}" ReRender="conpgblk" >
                        <apex:param assignTo="{!accId}" name="accname" value="{!ac.id}"/>
                    </apex:actionSupport>
                </apex:column>
                <apex:column value="{!ac.Name}" />
                <apex:column value="{!ac.AccountNumber}" />
            </apex:pageBlockTable>
        </apex:pageBlock>
        
        
        <div id="globaSearch" class="modal fade" role="dialog" width="100%">
            <div class="modal-dialog">
               <div class="modal-content">
                    <div class="modal-header">
                       <!-- <button type="button" class="close" data-dismiss="modal">&times;</button> -->
                        <h4 class="modal-title">Contacts</h4>
                    </div>
                    <div class="modal-body">      
                        <apex:pageBlock id="conpgblk" >
                            <apex:outputPanel rendered="{!conList.size == 0}">
                                <b> NO RELATED CONTACTS FOR THIS ACCOUNT .</b>
                            </apex:outputPanel>
                            <apex:outputPanel rendered="{!conList.size != 0}">
                                <apex:pageBlockTable value="{!conList}" var="con">
                                    <apex:column value="{!con.FirstName}" />
                                    <apex:column value="{!con.LastName}" />                                   
                                    <apex:column ><apex:facet name="header">Birthdate</apex:facet> <apex:inputField value="{!con.Birthdate}"/></apex:column>
                                    <apex:column ><apex:facet name="header">Department</apex:facet> <apex:inputField value="{!con.Department}"/></apex:column>
                                    <apex:column ><apex:facet name="header">Phone</apex:facet> <apex:inputField value="{!con.Phone}"/></apex:column>        
                                </apex:pageBlockTable>
                            </apex:outputPanel>
                         
                            <apex:commandButton value="Save" id="save"/> 
                        </apex:pageBlock>
                        
                    </div>
                    
                </div>
                
            </div>
        </div>
        
    </apex:form>
</apex:page>

It is fetching information of related contacts and unable to update save functionality .