When I hit enter in miltimode text box there is strange characters(square) are stored in sql database.I want to display that details on other pages so what should I do?

<%@ Page Language="C#" MasterPageFile="~/VisitorMaster.master" AutoEventWireup="true" CodeFile="city.aspx.cs" Inherits="Default4" Title="Untitled Page" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <table cellspacing="5" id="tbl" runat="server" width="100%">
    <tr>
        <td style="width:20%">
            <asp:Label ID="lblcityid" runat="server" Text="Id"></asp:Label>
        </td>
        <td style="width:80%">
            <asp:TextBox ID="txtcityid" runat="server"></asp:TextBox>
            <asp:RequiredFieldValidator ID="reqcityid" runat="server"
                ErrorMessage="Please Enter Id" ControlToValidate="txtcityid">*</asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td style="width:20%">
            <asp:Label ID="lblname" runat="server" Text="City Name"></asp:Label>
        </td>
        <td style="width:80%">
            <asp:TextBox ID="txtname" runat="server"></asp:TextBox>
            <asp:RequiredFieldValidator ID="reqname" runat="server"
                ErrorMessage="Please City Name" ControlToValidate="txtname">*</asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td style="width:20%">
            <asp:Label ID="lbldesc" runat="server" Text="Description"></asp:Label>
        </td>
        <td style="width:80%">
            <asp:TextBox ID="txtdesc" runat="server"></asp:TextBox>
            <asp:RequiredFieldValidator ID="reqdesc" runat="server"
                ErrorMessage="Please Enter Description" ControlToValidate="txtdesc">*</asp:RequiredFieldValidator>
        </td>
    </tr>
     <tr>
        <td style="width:20%">
            <asp:Label ID="lblstateid" runat="server" Text="State Name"></asp:Label>
        </td>
        <td style="width:80%">
            <asp:DropDownList ID="ddstateid" runat="server" AutoPostBack="True"
                DataSourceID="sqldtsrcstateid" DataTextField="vcname"
                DataValueField="nostateid">
            </asp:DropDownList>
            <asp:SqlDataSource ID="sqldtsrcstateid" runat="server"
                ConnectionString="<%$ ConnectionStrings:HTHConnStr %>"
                SelectCommand="SELECT [nostateid], [vcname] FROM [state]"></asp:SqlDataSource>
        </td>
    </tr>
    <tr>
        <td style="width:20%">
            <asp:Label ID="lblnolongitude" runat="server" Text="Longitude"></asp:Label>
        </td>
        <td style="width:80%">
            <asp:TextBox ID="txtnolongitude" runat="server"></asp:TextBox>
            <asp:RequiredFieldValidator ID="reqnolongitude" runat="server"
                ErrorMessage="Please Enter Longitude" ControlToValidate="txtnolongitude">*</asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td style="width:20%">
            <asp:Label ID="lblnolatitude" runat="server" Text="Latitude"></asp:Label>
        </td>
        <td style="width:80%">
            <asp:TextBox ID="txtnolatitude" runat="server"></asp:TextBox>
            <asp:RequiredFieldValidator ID="reqnolatitude" runat="server"
                ErrorMessage="Please Enter Latitude" ControlToValidate="txtnolatitude">*</asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td style="width:20%" valign="top">
            <asp:Label ID="lblhistory" runat="server" Text="History"></asp:Label>
        </td>
        <td style="width:80%">
            <asp:TextBox ID="txthistory" runat="server" TextMode="MultiLine" Height="176px"
                Width="350px"></asp:TextBox>
            <asp:RequiredFieldValidator ID="reqhistory" runat="server"
                ErrorMessage="Please Enter Latitude" ControlToValidate="txthistory">*</asp:RequiredFieldValidator>
        </td>
    </tr>
    <tr>
        <td colspan="2">
            &nbsp;<asp:ValidationSummary ID="vsummary" runat="server" Width="288px"
                Height="55px" />
        </td>
    </tr>
    <tr>
        <td colspan="2">
            &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
            <asp:Button ID="btnsubmit" runat="server" Text="Submit" onclick="Button1_Click" />
        </td>
    </tr>
</table>
</asp:Content>

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
public partial class Default4 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        DataClass dtcs = new DataClass();
        //string history = txthistory.Text;
        //history = history
        txthistory.Text = txthistory.Text.Replace("'", "''");
        string str;
        str = "INSERT INTO city (nocityid,nostateid,vcname,vcdesc,nolongitude,nolatitude,vchistory) VALUES ('" + txtcityid.Text + "','" + ddstateid.SelectedItem.Value + "','" + txtname.Text + "','" + txtdesc.Text + "','"+ txtnolongitude.Text +"','"+ txtnolatitude.Text +"','"+ txthistory.Text +"')";
        dtcs.execqry(str);
        txtcityid.Text = "";
        txtname.Text = "";
        txtdesc.Text = "";
        txthistory.Text = "";
        txtnolatitude.Text = "";
        txtnolongitude.Text = "";
    }
}