Add a New Item to a SharePoint List

Add a New Item to a List (.ACSX)

<!-- Assemblies, imports, and registrations go here -->
<table>
    <tr>
        <td>Drink Name:</td>
        <td>
            <asp:TextBox ID="TitleTextBox" runat="server"></asp:TextBox>
        </td>
    </tr>
    <tr>
        <td>Size:</td>
        <td>
            <asp:DropDownList ID="SizeDropDownList" runat="server">
                <asp:ListItem Text="Tall" Value="Tall" Selected="True" />
                <asp:ListItem Text="Grande" Value="Grande" />
                <asp:ListItem Text="Venti" Value="Venti" />
            </asp:DropDownList>
        </td>
    </tr>
    <tr>
        <td>Calories:</td>
        <td>
            <asp:TextBox ID="CaloriesTextBox" runat="server"></asp:TextBox>
        </td>
    </tr>
    <tr>
        <td>Seasonal?</td>
        <td>
            <asp:CheckBox ID="SeasonalCheckBox" runat="server" />
        </td>
    </tr>
    <tr>
        <td colspan="2"><asp:Button ID="SaveButton" runat="server" Text="Add" OnClick="Add_New" /></td>
    </tr>
</table>

Add a New Item to a List (.ACSX.CS)

using System;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using Microsoft.SharePoint;
 
namespace SampleProject.AddNewItem
{
    public partial class AddNewItemUserControl : UserControl
    {
        protected void Page_Load(object sender, EventArgs e)
        {
 
        } //end Page_Load
 
        protected void Add_New(object sender, EventArgs e)
        {
            //Select the list
            SPWeb thisWeb = SPContext.Current.Web;
            SPList sampleList = thisWeb.Lists["Starbucks"];
            
            //Add a new item to the list
            SPListItem item = sampleList.AddItem();
 
            //Store values entered into the textbox
            item["Title"] = TitleTextBox.Text;
            item["Size"] = SizeDropDownList.SelectedValue;
            item["Calories"] = Convert.ToInt32(CaloriesTextBox.Text);
            item["Seasonal"] = SeasonalCheckBox.Checked;
 
            //Finally, save
            item.Update();
            
            //Go to the list view
            Response.Redirect("http://localhost/sample/Lists/Starbucks/AllItems.aspx");
            
        } //end Add_New
    }
}