Keep Adding Data In Current Row Unless I Press The Clear Button To Change Row

public partial class WebForm5 : System.Web.UI.Page
  {
      protected void Page_Load(object sender, EventArgs e)
      {
          if (!(IsPostBack))
          {
              Session["List"] = null;
              ViewState["i"] = ViewState["j"] = 1;
              ViewState["state"] = "";


          }
      }
      public static DataTable dt;
      public static int i = 1;
      protected void txtName_Click(object sender, EventArgs e)
      {

          Session["List"] = dt;
          dt = new DataTable();
          DataRow dr = null;

          dt.Columns.Add(new DataColumn("RowNumber", typeof(int)));
          dt.Columns.Add(new DataColumn("Column1", typeof(string)));
          if (Session["List"] == null)
          {
              if (Convert.ToInt16(ViewState["i"]) == Convert.ToInt16(ViewState["j"]))
              {
                  dr = dt.NewRow();
                  dr["RowNumber"] = i;
                  dr["Column1"] = Convert.ToString(ViewState["state"]) + txtName.Text;
                  ViewState["state"] = Convert.ToString(ViewState["state"]) + txtName.Text;
                  dt.Rows.Add(dr);



              }
              grdData.DataSource = dt;
              grdData.DataBind();
          }

                if (Session["List"] != null)
              {
        if  ( Convert .ToInt16 ( ViewState["i"] )!=  Convert .ToInt16 ( ViewState["j"]))
          {


                  dt = (DataTable)Session["List"];
                  dr = dt.NewRow();
                  dr["Column1"] =  txtName.Text;
                  dr["RowNumber"] = i;

                  dt.Rows.Add(dr);
                  //lst = (List<string>)Session["List"];
                  //lst.Insert(i,txtAdd.Text);
                  //i++;
                  grdData.DataSource = dt;
                  grdData.DataBind();
              }
        else if (Convert.ToInt16(ViewState["i"]) == Convert.ToInt16(ViewState["j"]))
        {
            dt = (DataTable)Session["List"];
           ViewState["state"] = grdData.Rows[((grdData.Rows.Count) - 1)].Cells[1].Text;
           string i =Convert.ToString( ViewState["state"]);
           int j = dt.Rows.Count;
            dt.Rows[(dt.Rows.Count)-1]["Column1"] =Convert.ToString(ViewState["state"])+ txtName.Text;
            grdData.DataSource = dt;
            grdData.DataBind();
        }

              ViewState["i"] = ViewState["j"];
          }
         txtName.Text = "";


      }

      protected void btnClr_Click(object sender, EventArgs e)
      {
          ViewState["j"] = i++;
          ViewState["state"] = "";
         // txtName.Text = grdData.Rows[(grdData.Rows.Count - 1)].Cells[1].Text;

      }

      protected void btnnew_Click(object sender, EventArgs e)
      {

          dt.Rows[(grdData.Rows.Count - 1)]["Column1"] = txtName.Text;
          grdData.DataSource = dt;
          grdData.DataBind();
      }
  }