DDL SelectedValue Convert.ToDecimal is getting rounded up during SP Insert C#

<asp:RadioButtonList ID="skillLevelCmbo" runat="server" RepeatLayout="Table" RepeatDirection="Horizontal" CssClass="skillLevel" BackColor="#00f3ff">
     <asp:ListItem Value="2.5">2.5</asp:ListItem>
     <asp:ListItem Value="3.0">3.0</asp:ListItem>
     <asp:ListItem Value="3.5">3.5</asp:ListItem>
     <asp:ListItem Value="4.0">4.0</asp:ListItem>
     <asp:ListItem Value="4.5">4.5</asp:ListItem>
     <asp:ListItem Value="5.0">5.0</asp:ListItem>
     <asp:ListItem Value="5.5">5.5</asp:ListItem>
     <asp:ListItem Value="6.0">6.0</asp:ListItem>
 </asp:RadioButtonList>

protected void submitBtn_Click(object sender, EventArgs e)
        {
            //update UserConfirmation Table
            SqlConnection cn = new SqlConnection(ConfigurationManager.ConnectionStrings["FMLConnection"].ToString());
            SqlCommand cmd = new SqlCommand("dbo.spInsertUserProfileData", cn);
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@userName", HttpContext.Current.User.Identity.Name);
            cmd.Parameters.AddWithValue("@firstName", fnameTB.Text);
            cmd.Parameters.AddWithValue("@lastName", lnameTB.Text);
            cmd.Parameters.AddWithValue("@userPhoneNumber", phnTB.Text);
            cmd.Parameters.AddWithValue("@email", emailTB.Text);
            cmd.Parameters.AddWithValue("@userStreetAddress", addressTB.Text);
            cmd.Parameters.AddWithValue("@userCity", cityTB.Text);
            cmd.Parameters.AddWithValue("@userState", Convert.ToString(DropDownListState.SelectedValue));
            cmd.Parameters.AddWithValue("@userZipCode", zipCodeTB.Text);
            cmd.Parameters.AddWithValue("@userBirthDate", DateTime.Parse(birthDate.Text));
            cmd.Parameters.AddWithValue("@userYearsPlayed", Convert.ToInt32(noOfYearsTB.Text));

//This is the Paramater with the issues if the SelectedValue = 3.5, 4.0 gets inserted?
cmd.Parameters.AddWithValue("@userSkillLevel"(Convert.ToDecimal(skillLevelCmbo.SelectedValue)));

            cn.Open();
            IAsyncResult result = cmd.BeginExecuteNonQuery();
            try
            {
                Session.Add("RegistrationComplete", result.IsCompleted);
                cmd.EndExecuteNonQuery(result);
                Response.Redirect("~/MyAccount");
            }
            catch (Exception ex)
            {
                errorsOccured.Text = "An error occurred: " + ex.Message;
            }
            finally
            {
                cn.Close();
            }
        }