Compare list items SharePoint Foundation 2010

Question

How can compare one item list with others items list in the meaning of No duplicate values ??

if (item.Title != dp1.Text + tb2.Text)
                        {
                        item["Title"] = dp1.Text + tb2.Text;
                        item["Nom"] = nom;
                        //item1["Date"] = DateTime.Now;
                        item["Qualification"] = qul;
                        item["Sit.Fam"] = sf;
                        item.Update();    
                            }
                            else
                            {
                                Console.WriteLine("Bulletin déja créer");  
                            }

Answer 1

I would suggest to use CAML query with Equal statement with your possible string concatenations that meets the requirement.

more details can be found in the below article and it's not a good practice to loop each item to compare.

https://msdn.microsoft.com/en-us/library/office/ee534956(v=office.14).aspx

Answer 2

Update your code as below,

    SPQuery myquery = new SPQuery();
        myquery.Query = "<Where>" +                       
                        "<Eq>"+
                        "<FieldRef Name='Title' />"+
                        "<Value Type='Text'>"+
                         dp1.Text + tb2.Text  +
                        "</Value>" +
                        "</Eq>" +                             
                        "</Where>";
      SPListItemCollection items = list.GetItems(myquery);
    If(items.count > 0)
    {
                            item["Title"] = dp1.Text + tb2.Text;
                            item["Nom"] = nom;
                            //item1["Date"] = DateTime.Now;
                            item["Qualification"] = qul;
                            item["Sit.Fam"] = sf;
                            item.Update();
    }
   else
                            {
                                Console.WriteLine("Bulletin déja créer");  
                            }