"Timeout expired This may have occurred becuse of max pool size was reached"

Hello i have this problem occur when i execute the following code
"Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached."
protected void gridoutofstock_RowDataBound(object sender, GridViewRowEventArgs e) { StoreClass s = new StoreClass(); try { for (int index = 0; index < this.gridoutofstock.Rows.Count; index++) { //here each method connect to the database and close it in StoreClass string sales= s.countproductinorders(this.gridoutofstock.Rows[index].Cells[0].Text); string service=s.countproductinservice(this.gridoutofstock.Rows[index].Cells[0].Text); string agreement=s.countproductinagreement(this.gridoutofsto ...