Object must implement IConvertible using ASP.NET - asp.net

Question

i'm experiencing this error called Object must implement IConvertible.
please help me!
i think it is because of the drop down list for user type. even if i delete / comment out the drop down list i am still experiencing this error.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
public partial class Admin_Register : System.Web.UI.Page
{
SqlConnection con = new SqlConnection(Helper.GetCon());
protected void Page_Load(object sender, EventArgs e)
{
GetUserTypes();
}
void GetUserTypes()
{
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandText = "SELECT TypeID, TypeName FROM UserTypes";
SqlDataReader data = cmd.ExecuteReader();
ddlUserTypes.DataSource = data;
ddlUserTypes.DataTextField = "TypeName";
ddlUserTypes.DataValueField = "TypeID";
ddlUserTypes.DataBind();
con.Close();
}
bool IsRecordExisting(string email)
{
bool existing = true;
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandText = "SELECT EmailAddress FROM Users WHERE EmailAddress=#EmailAddress";
cmd.Parameters.Add("#EmailAddress", SqlDbType.VarChar).Value = email;
SqlDataReader data = cmd.ExecuteReader();
if (data.HasRows)
existing = true;
else
existing = false;
con.Close();
return existing;
}
protected void btnRegister_Click(object sender, EventArgs e)
{
if (!IsRecordExisting(txtEmail.Text))
{
con.Open();
SqlCommand cmd = new SqlCommand();
cmd.Connection = con;
cmd.CommandText = "INSERT INTO Users VALUES (#EmailAddress, #Password, #TypeID, #FirstName, #LastName, #MiddleInitial, #Address, #TelNo, #CelNo, #Status";
cmd.Parameters.Add("#EmailAddress", SqlDbType.VarChar).Value = txtEmail.Text;
cmd.Parameters.Add("#Password", SqlDbType.VarChar).Value = Helper.CreateSHAHash(txtPassword.Text);
cmd.Parameters.Add("#TypeID", SqlDbType.Int).Value = ddlUserTypes.SelectedValue;
cmd.Parameters.Add("#FirstName", SqlDbType.VarChar).Value = txtFN;
cmd.Parameters.Add("#LastName", SqlDbType.VarChar).Value = txtLN;
cmd.Parameters.Add("#MiddleInitial", SqlDbType.VarChar).Value = "";
cmd.Parameters.Add("#Address", SqlDbType.VarChar).Value = "";
cmd.Parameters.Add("#TelNo", SqlDbType.VarChar).Value = "";
cmd.Parameters.Add("#CelNo", SqlDbType.VarChar).Value = "";
cmd.Parameters.Add("#Status", SqlDbType.VarChar).Value = "Active";
cmd.ExecuteNonQuery();
con.Close();
Helper.Log("0", "Register", "User Registration");
Helper.ClearTextboxes(this.Controls);
register.Visible = true;
}
else
{
register.Visible = false;
error.Visible = true;
}
}
}

Answer 1

I found two problems in your code
First
Please check these lines
cmd.Parameters.Add("#FirstName", SqlDbType.VarChar).Value = txtFN;
cmd.Parameters.Add("#LastName", SqlDbType.VarChar).Value = txtLN;
You are setting parameter value as Texbox. You need to set text of the textbox as parameter values.
cmd.Parameters.Add("#FirstName", SqlDbType.VarChar).Value = txtFN.Text;
cmd.Parameters.Add("#LastName", SqlDbType.VarChar).Value = txtLN.Text;
Second
Dropdown list SelectedValue property return string value. That menas you need to convert string value to int type at assigning time.
Please change this line
cmd.Parameters.Add("#TypeID", SqlDbType.Int).Value = ddlUserTypes.SelectedValue;
to
cmd.Parameters.Add("#TypeID", SqlDbType.Int).Value = Convert.ToInt32(ddlUserTypes.SelectedValue);