generate multi-column table through the cycle of reading DataReader

int toShowColumn = 4;
System.Text.StringBuilder sb = new System.Text.StringBuilder();
string cnString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=DataDirectory\aspxWeb.mdb;";
OleDbConnection cn = new OleDbConnection(cnString);
cn.Open();
OleDbCommand cmd = new OleDbCommand("Select * from Document", cn);
OleDbDataReader dr = cmd.ExecuteReader();
sb.Append("");
while (dr.Read())
{
sb.Append("");
sb.Append("");
for (int i = 0; i < toShowColumn - 1; i++)
{
if (dr.Read())
{
sb.Append("");
}
else
{
sb.Append("");
}
}
sb.Append("");
}
sb.Append("

"); sb.Append(dr["Title"].ToString()); sb.Append("

"); sb.Append(dr["Title"].ToString()); sb.Append("

");
div1.InnerHtml = sb.ToString();
dr.Close();
cn.Close();
cn.Dispose();