how to use "IsPostBack" & ViewState in c# windows appli..

Question

public Form2()

{

InitializeComponent();

if (!this.IsPostBack)

{

DataTable dt = new DataTable();

dt.Columns.AddRange(new DataColumn[2] { new DataColumn("Name"), new DataColumn("Country") });

ViewState["Customers"] = dt;

this.BindGrid();

}

}

 

protected void BindGrid()

{

dataGridView.DataSource = (DataTable)ViewState["Customers"];

dataGridView.DataBind();

}

 

Error show in red highlight