Remove session variable when closing popup

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C#5.0

My Run page as follows


My Gridview page code as follows

My Gridview code as follows

protected void Page_Load(object sender, EventArgs e)
{

using (var con = new SqlConnection(ConfigurationManager.ConnectionStrings["himtConnectionString"].ConnectionString))


using (var cmd = new SqlCommand("OH_PKG_DATE_COMBINATION '" + Session["compkgid"].ToString().Trim() + "'", con))

con.Open();
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
GridView1.DataSource = dt;
GridView1.DataBind();
}

Lnk button code as follows

   protect void Link_click(object sender,eventargs e)
{
     popup.show();
}

In Link button from the session variable data will be passed in gridview using the popup.

Link Button (To View Available Batch Date)

When i click the View Available Batch date in Link button Pop up will be shown.

POP up as follows

Show date (Button)

When i click the Show date button in popup then in Gridview date will be displayed.

Then i have one button called Hide Button.

When i click the hide button i want to clear the session variable.

i want to clear Session["compkgid"] values when i click the hide button in popup.

for that how can i do.