Call Server Side event on HTML Input Button Click using C# and VB.Net in ASP.Net

hi,

I define submit input in page:

 <input type="submit" class="btn btn-primary" value="Send Message"/>

I want when users click on this input it inserts data into the database I did it with button control:

<asp:ImageButton ID="Imgsend" runat="server" ImageUrl="~/Image/main/sendmessage.png" CssClass="imgSeneMe" OnClick="Imgsend_Click"></asp:ImageButton> 

protected void Imgsend_Click(object sender, ImageClickEventArgs e)
{
    bool isValid = aspcap.Validate(Txtc.Text.Trim());
    if (isValid)
    {
        using (SqlConnection conn = General.GetConnection())
        {
            using (SqlCommand _cmd = General.GetCommand("MessageNew_insertInfo", conn))
            {
                conn.Open();
                _cmd.Parameters.AddWithValue("@Topic", Txttopic.Text);
                _cmd.Parameters.AddWithValue("@Name", Txtname.Text);
                _cmd.Parameters.AddWithValue("@Description", Txtdes.Text);
                _cmd.ExecuteNonQuery();
            }
        }
    }
  
}

now I want to do like above code for input

how I can do it?

Best regards

Neda