C# 实现基于ADO.NET框架的DBHelper工具类(简化数据库操作)

namespace Test
{
    public static class DBHelper
    {
        // 请根据实际情况设置数据库连接字符串
        private static readonly string connectionString = "your_connection_string_here";
        /// <summary>
        /// 执行一个查询，返回结果集中第一行的第一列。
        /// </summary>
        public static int GetScalar(string sql, SqlParameter[] parameters = null)
        {
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    if (parameters != null)
                    {
                        cmd.Parameters.AddRange(parameters);
                    }
                    conn.Open();
                    object result = cmd.ExecuteScalar();
                    return result != null ? Convert.ToInt32(result) : 0;
                }
            }
        }
        /// <summary>
        /// 执行一个查询，返回一个数据读取器(SqlDataReader)。
        /// </summary>
        public static SqlDataReader GetReader(string sql, SqlParameter[] parameters = null)
        {
            SqlConnection conn = new SqlConnection(connectionString);
            SqlCommand cmd = new SqlCommand(sql, conn);
            if (parameters != null)
            {
                cmd.Parameters.AddRange(parameters);
            }
            conn.Open();
            return cmd.ExecuteReader(CommandBehavior.CloseConnection);
        }
        /// <summary>
        /// 执行一个查询，返回一个数据集(DataTable)。
        /// </summary>
        public static DataTable GetDataSet(string sql, SqlParameter[] parameters = null)
        {
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    if (parameters != null)
                    {
                        cmd.Parameters.AddRange(parameters);
                    }
                    using (SqlDataAdapter da = new SqlDataAdapter(cmd))
                    {
                        DataTable dt = new DataTable();
                        da.Fill(dt);
                        return dt;
                    }
                }
            }
        }
        /// <summary>
        /// 执行一个命令(Insert, Update, Delete)，返回受影响的行数。
        /// </summary>
        public static int ExecuteCommand(string sql, SqlParameter[] parameters = null)
        {
            using (SqlConnection conn = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    if (parameters != null)
                    {
                        cmd.Parameters.AddRange(parameters);
                    }
                    conn.Open();
                    return cmd.ExecuteNonQuery();
                }
            }
        }
    }
}

string insertSql = "INSERT INTO Users (UserName, Password) VALUES (@UserName, @Password)";
SqlParameter[] insertParams = {
    new SqlParameter("@UserName", SqlDbType.VarChar, 50) { Value = "JohnDoe" },
    new SqlParameter("@Password", SqlDbType.VarChar, 50) { Value = "SecretPassword" }
};
int rowsAffected = DBHelper.ExecuteCommand(insertSql, insertParams);

string updateSql = "UPDATE Users SET Password = @Password WHERE UserName = @UserName";
SqlParameter[] updateParams = {
    new SqlParameter("@UserName", SqlDbType.VarChar, 50) { Value = "JohnDoe" },
    new SqlParameter("@Password", SqlDbType.VarChar, 50) { Value = "NewPassword" }
};
int rowsAffected = DBHelper.ExecuteCommand(updateSql, updateParams);

string deleteSql = "DELETE FROM Users WHERE UserName = @UserName";
SqlParameter[] deleteParams = {
    new SqlParameter("@UserName", SqlDbType.VarChar, 50) { Value = "JohnDoe" }
};
int rowsAffected = DBHelper.ExecuteCommand(deleteSql, deleteParams);

string sql = "SELECT * FROM Users WHERE UserName LIKE @UserName";
SqlParameter[] parameters = {
    new SqlParameter("@UserName", SqlDbType.VarChar, 50) { Value = "%Doe%" }
};
DataTable users = DBHelper.GetDataSet(sql, parameters);

string sql = "SELECT COUNT(*) FROM Users WHERE UserName = @UserName";
SqlParameter[] parameters = {
    new SqlParameter("@UserName", SqlDbType.VarChar, 50) { Value = "JohnDoe" }
};
int userCount = DBHelper.GetScalar(sql, parameters);

string sql = "SELECT UserName, Password FROM Users WHERE UserName = @UserName";
SqlParameter[] parameters = {
    new SqlParameter("@UserName", SqlDbType.VarChar, 50) { Value = "JohnDoe" }
};
using (SqlDataReader reader = DBHelper.GetReader(sql, parameters))
{
    while (reader.Read())
    {
        string userName = reader["UserName"].ToString();
        string password = reader["Password"].ToString();
        // 处理数据
    }
}