Save TextBox value in Database using C# in ASP.Net

Dear Sir,

While I have  save data in table , It's intered "System.Web.UI.WebControls.TextBox " in table . Please help me to remove this.

HTML

<div class="modal fade" id="myModal19" role="dialog">
    <div class="modal-dialog">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal">&times;</button>
                <h4 class="modal-title">Walkie Talkie</h4>
            </div>
            <div class="modal-body">
                <b>
                    <p>Available Stocks</p>
                </b>
                Total : Issued :
                    <br />
                <br />
                <asp:Label ID="Label22" runat="server" Text="USER-1"></asp:Label><br />
                <br />
                <table border="0" width="570">
                    <tr>
                        <td>Asset No:<br />
                            <asp:TextBox ID="TextBox1_Wlke_tlke" runat="server" BackColor="WhiteSmoke"></asp:TextBox>
                        </td>
                        <td>Asset Name:<br />
                            <asp:TextBox ID="TextBox2_Wlke_tlke" Text="Walkie_Talkie" runat="server" BackColor="Wheat"></asp:TextBox>
                        </td>
                    </tr>
                    <tr>
                        <td>Serial Number:<br />
                            <asp:TextBox ID="TextBox3_Wlke_tlke" runat="server" BackColor="WhiteSmoke"></asp:TextBox>
                        </td>
                        <td>Date:<br />
                            <asp:TextBox ID="TextBox4_Wlke_tlke" runat="server" BackColor="Wheat"></asp:TextBox>
                        </td>
                    </tr>
                    <tr>
                        <td>Make Model:<br />
                            <asp:TextBox ID="TextBox5_Wlke_tlke" runat="server" BackColor="WhiteSmoke"></asp:TextBox>
                        </td>
                        <td>PO. Number:<br />
                            <asp:TextBox ID="TextBox6_Wlke_tlke" runat="server" BackColor="WhiteSmoke"></asp:TextBox>
                        </td>
                    </tr>
                </table>
            </div>
        </div>
    </div>
</div>

C#

protected void Button_Wlk_Tlke_Click(object sender, EventArgs e)
{
    string cs = System.Configuration.ConfigurationManager.ConnectionStrings["constr"].ConnectionString;

    SqlConnection con = new SqlConnection(cs);

    SqlCommand cmd = new SqlCommand("INSERT INTO wlk_tlke (empid,asset_no,asset_nm,srl_num,dt,mk_mdl,po_nm) VALUES('" + Label22.Text + "','" + TextBox1_Wlke_tlke + "','" + TextBox2_Wlke_tlke.Text + "','" + TextBox3_Wlke_tlke.Text + "','" + TextBox4_Wlke_tlke.Text + "','" + TextBox5_Wlke_tlke.Text + "','" + TextBox6_Wlke_tlke.Text + "')", con);

    con.Open();

    cmd.ExecuteNonQuery();

    con.Close();
    TextBox1_Wlke_tlke.Text = "";
    TextBox2_Wlke_tlke.Text = "";
    TextBox3_Wlke_tlke.Text = "";
    TextBox4_Wlke_tlke.Text = "";
    TextBox5_Wlke_tlke.Text = "";
    TextBox6_Wlke_tlke.Text = "";

}