Saving CKEditor data to database in ASP.Net

<%@ Page Title="" Language="C#" MasterPageFile="~/Admin.master" AutoEventWireup="true" CodeFile="new_article.aspx.cs" Inherits="post_article" validateRequest="false" %>
<%@ Register Assembly="CKEditor.NET" Namespace="CKEditor.NET" TagPrefix="CKEditor" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
   <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<script type="text/javascript" src="~/ckeditor/ckeditor.js"></script>
<script type="text/javascript" src="~/ckeditor/adapters/jquery.js"></script>
   
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <div class="content">
       <asp:TextBox ID="txtTitle" CssClass="txtTitle" runat="server" placeholder="Enter title here..."></asp:TextBox>
        
        <p style="width:80%; margin:10px;">
            <CKEditor:CKEditorControl ID="txtPost"  Height="200" BasePath="~/ckeditor/"  runat="server" Toolbar="Basic" ClientIDMode="Inherit">
           </CKEditor:CKEditorControl>
        </p>

        <asp:Button ID="btnPost" CssClass="btn" runat="server" Text="Post" OnClick="btnPost_Click" />

        <asp:Label ID="lblStatus" runat="server" Text=""></asp:Label>
    </div>

        
</asp:Content>

protected void btnPost_Click(object sender, EventArgs e)
    {

        string str = HttpUtility.HtmlEncode(txtPost.Text);
        
        //perform user defined checks
        if (txtTitle.Text == "" || txtPost.Text == "")
        {
            lblStatus.Text = "Title or Post Content is Missing !";
        }
        else
        {
            string insertSQL = "INSERT INTO user_posts (";
            insertSQL += "post_title, post_data, post_date, user_id) ";
            insertSQL += "VALUES (";
            insertSQL += "@post_title, @post_data, GETDATE(), @user_id) ";

            SqlConnection con = new SqlConnection(@"Data Source=(LocalDB)\v11.0;AttachDbFileName=|DataDirectory|\Database.mdf;Integrated Security=True;MultipleActiveResultSets=True");
            SqlCommand cmd = new SqlCommand(insertSQL, con);

            //Add Parameters
            cmd.Parameters.AddWithValue("@post_title", txtTitle.Text);
            cmd.Parameters.AddWithValue("@post_data", str);
            cmd.Parameters.AddWithValue("@user_id", "1");

            //Insertion
            int added = 0;

            try
            {
                con.Open();
                added = cmd.ExecuteNonQuery();
                lblStatus.Text = "Article Posted Successfully !";
            }

            catch (Exception err)
            {
                lblStatus.Text = err.Message;
            }
        }


    }

string str = txtPost.Text

string str = HttpUtility.HtmlEncode(txtPost.Text);

CREATE TABLE [dbo].[user_posts] (
    [post_id]    INT           IDENTITY (1, 1) NOT NULL,
    [post_title] VARCHAR (50)  NOT NULL,
    [post_data]  VARCHAR (MAX) NOT NULL,
    [post_date]  DATE          NOT NULL,
    [user_id]    INT           NOT NULL,
    PRIMARY KEY CLUSTERED ([post_id] ASC),
    FOREIGN KEY ([user_id]) REFERENCES [dbo].[user_details] ([user_id])
);