string connectionString = "Server=localhost;Database=YourDatabase;Integrated Security=True;";
// 或使用SQL身份验证
string connectionString = "Server=localhost;Database=YourDatabase;User Id=username;Password=password;";

string connectionString = "Server=localhost\\InstanceName;Database=YourDatabase;Integrated Security=True;";

using System;
using System.Data.SqlClient;

class Program
{
    static void Main()
    {
        string connectionString = "Server=localhost;Database=YourDatabase;Integrated Security=True;";
        
        try
        {
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();
                Console.WriteLine("连接成功!");
                
                // 执行查询示例
                string query = "SELECT COUNT(*) FROM YourTable";
                using (SqlCommand command = new SqlCommand(query, connection))
                {
                    int count = (int)command.ExecuteScalar();
                    Console.WriteLine($"表中记录数: {count}");
                }
            }
        }
        catch (SqlException ex)
        {
            Console.WriteLine($"SQL错误: {ex.Message}");
            Console.WriteLine($"错误号: {ex.Number}");
        }
        catch (Exception ex)
        {
            Console.WriteLine($"错误: {ex.Message}");
        }
    }
}