Ошибка в работе со строкой в запросе

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
 
namespace WindowsFormsApp2
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }
 
        private void Button1_Click(object sender, EventArgs e)
        {
            Form1 f1 = new Form1();
            f1.Show();
            this.Close();
        }
 
        private void Button2_Click(object sender, EventArgs e)
        {
            string name = textBox1.Text;
            string age = Convert.ToString(numericUpDown1.Value);
            string connectionString = @"DataSourse =. \SQLEXPRESS; Inital Catalog=usersdb; Integrated Security = true";
            string sqlCommand = ("INSERT INTO Users (Name, Age) VALUES({0},{1})", name, age);
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand command = new SqlCommand(sqlCommand, connection))
                {
                    connection.Open();
 
                    connection.Close();
                }
            }
        }
    }
}

string connectionString = @"DataSourse =. \SQLEXPRESS; Inital Catalog=usersdb; Integrated Security = true";
using (SqlConnection sqlConnection = new SqlConnection(connectionString))
{
    string sqlText = "INSERT INTO Users VALUES(@name, @age)"
    SqlCommand comm = new SqlCommand(sqlText, sqlConnection);
    comm.Parameters.AddWithValue("@name", textBox1.Text.ToString());
    comm.Parameters.AddWithValue("@age", numericUpDown1.Value.ToString());
 
    sqlConnection.Open();
    comm.ExecuteNonQuery();
    sqlConnection.Close();
}

string sqlCommand = String.Format("INSERT INTO Users (Name, Age) VALUES('{0}','{1}')", name, age);