I am fetching data from server in 2 steps .
First is fetch randomly 25 records from my table and show that records to user , now i have added a button . when user click on that button i have to show next 25 records from database but i need to sure that these records doesn't contains anyone which is already been displayed . How to do this in c#
Here is the code by which i get first 25 records
var records = context.couponservice.Query().Take(25).ToList();
thanks in advance .
You can use .Skip(pageSize * numberOfPages) before the .Take(pageSize) to skip however many records/pages you don't want to show.
How about
int position = 25; // Increase this for each page
var nextRecords = context.couponservice.Query().Skip(position).Take(25).ToList();
Try this
for(i=0;i<noOfPages;i++)
{
var records = context.couponservice.Query().Skip(i * 25).Take(25).ToList();
}
This will give you every time new records.
Keep track of which items you've already fetched. For example store the ID's in a List or something. Then collect only the items from your source whose ID is not in the List. From that result you can select 25 random items.
For example:
//Your datasource
var source = new Dictionary<int, string>
{
{1, "One"},
{2, "Two"},
{3, "Three"},
{4, "Four"},
{5, "Five"},
{6, "Six"},
{7, "Seven"},
{8, "Eight"},
{9, "Nine"},
{10, "Ten"}
};
//The ID's of already fetched items
var taken = new List<int> { 2, 7, 3, 6 };
//Subset: all items that haven't been taken yet:
var temp = source.Where(s => taken.Contains(s.Key) == false);
From 'temp' you can select random elements now and add the ID's of those items to the List 'taken'.
Skip()andTake()solutions below, I'd strongly advise also adding anOrderBy()