Hi All
I have developed a class for file uploading.its working fine me now.but i want to put restriction that without file upload record couldnot save.if i am going for save record without file uplaod it will showing error message.how to solve this
 

public class FormCurriculumController { 
  

public Purchase_Order__c curriculum {get; set;}
public Boolean privacy {get; set;}
public Boolean saved {get; set;}
public String styleClass {get; set;}

public Transient Blob resume {get; set;}
public String contentType {get; set;}
public String fileName {get; set;}
      
    public boolean showC1RecordType {get;set;}
    public boolean showC2RecordType {get;set;} 
    
    private Id c1RecordTypeId; 
    private Id c2RecordTypeId;


//ublic FormCurriculumController () {
    //curriculum = new Purchase_Order__c();
    //saved = false;
//}

  public FormCurriculumController(ApexPages.StandardController controller) {

        c1RecordTypeId = Schema.SObjectType.Purchase_Order__c.getRecordTypeInfosByName().get('C1').getRecordTypeId();
        c2RecordTypeId = Schema.SObjectType.Purchase_Order__c.getRecordTypeInfosByName().get('C2').getRecordTypeId();
        
        curriculum= new Purchase_Order__c();
        curriculum= (Purchase_Order__c)controller.getRecord();
         
        String isButtonClicked = Apexpages.currentPage().getParameters().get('setDefaultValues');
        if(isButtonClicked == 'true'){
            setDefaultValues();
        }
        
        showC1RecordType = false;
        showC2RecordType = false;
       
        if(curriculum.RecordTypeId == c1RecordTypeId){
            showC1RecordType = true;
            showC2RecordType = false;
        }
        else if(curriculum.RecordTypeId == c2RecordTypeId){
            showC1RecordType = false;
            showC2RecordType = true;
        }
        
    }
    
     public void setDefaultValues(){
        String quoteId = Apexpages.currentPage().getParameters().get('quoteId');
        Quote__c quote = [Select o.id, o.name, o.Quantity_formula__c, o.Opportunity_Product_Detail__r.Opportunity__c,
                    o.Opportunity__c, o.Record_type_name__c,o.Company_Name__c,Opportunity_Product_Detail__r.Opportunity__r.Account__c from Quote__c o WHERE O.id=:quoteId];
        //system.assert(false,quote);     
        curriculum.Opportunity__c = quote.Opportunity_Product_Detail__r.Opportunity__c;
        curriculum.Quote__c = quote.id;
        curriculum.Company__c = quote.Opportunity_Product_Detail__r.Opportunity__r.Account__c;
        
        if(quote.Record_type_name__c == 'C1'){
            curriculum.RecordTypeId = c1RecordTypeId;
        }
        else {
            curriculum.RecordTypeId = c2RecordTypeId;
        }
    }

    


public PageReference save() {
    try {
     
        if (!privacy) {
        
             ApexPages.Message reqMsg = new ApexPages.Message(ApexPages.Severity.ERROR,'Please upload recent Purchase Order  before saving the record');
                ApexPages.addMessage(reqMsg);
            return null;
        }


        
       
        
        if( ! Test.isRunningTest() )
        {   
            insert(curriculum);
        }
        
        if (resume != null) {
            Attachment attach = new Attachment();
            attach.Body = resume;
            attach.Name = fileName;
            attach.ContentType= contentType;
            attach.ParentId = curriculum.id;                
            try {
                
               
                insert(attach);
                return new PageReference('/'+curriculum.id);

            } catch (Exception ex) {
               

                ApexPages.addMessages(ex);
                return null;
            }                    
        }

        update curriculum;

        saved = true;

    } 
    catch(Exception ex) {
        ApexPages.addMessages(ex);  
    }
    return null;   
}
}