How to solve System.OutOfRange exception for below code

Question

 // Sorce Code  //

using System.Data;

using System.Data.SqlClient;

 

namespace ASPNET

{

public partial class company : System.Web.UI.Page

{

DataSet ds;

int RowIndex=0;

protected void Page_Load(object sender, EventArgs e)

{

if (!IsPostBack)

{

SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;Database=SagarDB;Integrated Security=SSPI");

SqlDataAdapter da = new SqlDataAdapter("Select ID,FirstName,LastName,Gender,Salary from company", con);

ds = new DataSet();

ShowData();

da.Fill(ds, "company");

Session["CDS"] = ds;

Session["RowIndex"] = RowIndex;

}

else

{

ds = (DataSet)Session["CDS"];

RowIndex = (int)Session["RowIndex"];

}

}

private void ShowData()

{

txtId.Text = ds.Tables[0].Rows[RowIndex]["ID"].ToString();

txtFName.Text = ds.Tables[0].Rows[RowIndex]["FirstName"].ToString();

txtLName.Text= ds.Tables[0].Rows[RowIndex]["LastName"].ToString();

txtGender.Text= ds.Tables[0].Rows[RowIndex]["Gender"].ToString();

txtSalary.Text= ds.Tables[0].Rows[RowIndex]["Salary"].ToString();

}

protected void btnFirst_Click(object sender, EventArgs e)

{

RowIndex = 0;

ShowData();

Session["RowIndex"] = RowIndex;

}

protected void btnPrev_Click(object sender, EventArgs e)

{

if(RowIndex>0)

{

RowIndex -= 1;

ShowData();

Session["RowIndex"] = RowIndex;

}

else

{

Response.Write("<script>alert('First Record of table')</script>");

}

}

protected void btnNext_Click(object sender, EventArgs e)

{

if(RowIndex<ds.Tables[0].Rows.Count-1)

{

RowIndex += 1;

ShowData();

Session["RowIndex"] = RowIndex;

}

else

{

Response.Write("<script>alert('Last Record of table')</script>");

}

}

protected void btnLast_Click(object sender, EventArgs e)

{

RowIndex = ds.Tables[0].Rows.Count - 1;

ShowData();

Session["RowIndex"] = RowIndex;

}

}

}