dynamically created checkboxes in gridview

Even youre adding the controls through <ItemTemplate>
it will automatically maintains the ViewState property,
but in your case it is the matter of Binding data to youe GrideView,
Check where you are binding the data.. In postback you shouldn't bind the data again (as it is similar to complete page refresh)
hense if you use Page_load() to bind the data, then you have to make condition for postback..
As shown

protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)//not for postbacks
            {
                GV.DataSource = CreateDataSource();
                GV.DataBind();
            }
        }

So for post backs the data will get from LoadPostBack()

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