How to prevent values from getting overwritten in session?

Question

I have repeater control with editlink button.The same page is opened in two tabs of same browser logged in with same user.On editing the repeater control , the IssueID value is stored in session inside repeater_ItemCommand() event.... like Session["IssueID"] = gvIssues.DataKeys[row.RowIndex].Values["IssueID"].ToString();

The repeater control is inside the gridview.

when user edits different records in both the browser at the same time or one after the other the .The second record IssueID value is overwritten with first IssueID value. On updating the records,same values are updated in the both the records .

There is conflict in updation of the records.

How an i update different record values at same time .

Can anyone please let me know,if there is alternative solution for this.

Thanks in advance