Asp.net mvc entity framework 4.1 saving on sub model codefirst

ok i have model

    public long prop1 { get; set; }   
 
     [Required] 
     public string prop2 { get; set; }
 
     [Required]    
     public string prop3 { get; set; }      
 
     [Required]  
     public string prop4 { get; set; }  
 

this table is the part of database generated from code first.

now the requirement arises that there will be a form with prop3 only and after submitting it it will be updated on the bases of prop1. how will i make it work with regard to creation of model and dbcontext? what is the usual practise here?

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