regarding checkbox

Question

i am developing a online project where  question is showing in a label and ans are shoing in a checkbox here i am using viewstate codes for next and previous buttoni want that if user click a check box ans saved to datbase and click next button question will be changed but if user click previous button the previous ques will display with user click here all i am going right but the code is not remembring the user click  i am posting my code please help me out 

protected void Button55_Click(object sender, EventArgs e)
{

ans1.Checked = false;
ans2.Checked = false;
ans3.Checked = false;
ans4.Checked = false;
string cs = WebConfigurationManager.ConnectionStrings["LocalSqlServer"].ConnectionString;
SqlConnection cn = new SqlConnection(cs); 
cn.Open();
DropDownList2.SelectedIndex = 0; 
SqlDataAdapter da3 = new SqlDataAdapter("select * from reasoning_en", cn);
da3.Fill(ds2, "reasoning_en");
i = Convert.ToInt32(ViewState["i"])-1;
SqlDataAdapter da = new SqlDataAdapter("select * from reasoning_en", cn);
da.Fill(ds, "reasoning_en");
ViewState["i"] = (int)ViewState["i"]-1;
DataSet ds6 = new DataSet();
SqlDataAdapter da6 = new SqlDataAdapter("select * from " + Label12.Text + "", cn);
da6.Fill(ds6, Label12.Text);

string m = ds6.Tables[0].Rows[i]["ans"].ToString().Trim();
if (m == ans1.Text)
{
ans1.Checked = true;
}

else if (m == ans2.Text)
{
ans2.Checked = true;
}
else if (m == ans3.Text)
{
ans3.Checked = true;
}
else if (m == ans4.Text)
{
ans4.Checked = true;
}

else
{
ans.Checked = true;
}

if (ds != null && (int)ViewState["i"] < ds.Tables[0].Rows.Count)
{
if (ds.Tables[0].Rows[i]["quesno"].ToString().Trim() == "1")
{

prev.Visible = false;
}

q0.Text = ds.Tables[0].Rows[i]["quesno"].ToString();
ques.Text = ds.Tables[0].Rows[i]["ques"].ToString();
ans1.Text = ds.Tables[0].Rows[i]["ans1"].ToString();
ans2.Text = ds.Tables[0].Rows[i]["ans2"].ToString();
ans3.Text = ds.Tables[0].Rows[i]["ans3"].ToString();
ans4.Text = ds.Tables[0].Rows[i]["ans4"].ToString();
ans.Text = ds.Tables[0].Rows[i]["ans5"].ToString(); 
String s = "select quesimg from reasoning_en where quesno='" + q0.Text + "'";
SqlCommand cmd = new SqlCommand(s, cn);
String path = Server.MapPath("~\\images\\");
SqlDataReader dr;
dr = cmd.ExecuteReader();
dr.Read();
Image1.Visible = true;//image control will now be visible.
Image1.ImageUrl = dr["quesimg"].ToString();//stores the image url to corresponding image contol and here Image1 is the id of the image control used
cn.Close();



}
else
{

}

cn.Close();
}