c# - asp.net 中第三层(数据访问层)的 Db Manager 类

Question

我正在按照 3 层架构构建网站。为此，我创建了一个名为 DB Manager 的类。

这是类

namespace DAL
{
    class DBManager
    {
        private static DataTable dt = new DataTable();
        private static string ConnectionString = System.Configuration.ConfigurationManager.AppSettings["SQLSERVER"];

        public static int ExecuteNonQuery(string query)
        {
            int result;
            SqlConnection con = new SqlConnection(ConnectionString);
            SqlCommand command = new SqlCommand(query, con);

            try
            {
                con.Open();
                result = command.ExecuteNonQuery();
                con.Close();
            }
            catch
            {
                result = -1;
            }
            finally
            {
                con.Close();
            }

            return result;
        }

        public static DataTable ExecuteDataTable(string query)
        {
            SqlConnection con = new SqlConnection(ConnectionString);
            SqlDataAdapter da = new SqlDataAdapter();
            dt = new DataTable();

            try
            {
                con.Open();
                da.SelectCommand = new SqlCommand(query, con);
                con.Close();
                da.Fill(dt);
            }
            catch
            {
                dt.Rows.Clear();
            }

            return dt;
        }

        public static string ExecuteScaler(string query)
        {
            SqlConnection con = new SqlConnection(ConnectionString);
            SqlDataAdapter da = new SqlDataAdapter();
            string result = string.Empty;

            try
            {
                con.Open();
                da.SelectCommand = new SqlCommand(query, con);
                con.Close();
                dt = new DataTable();
                da.Fill(dt);

                if (dt.Rows.Count == 1 && dt.Columns.Count == 1)
                {
                    result = dt.Rows[0][0].ToString();
                }

            }
            catch
            {
                result = string.Empty;
            }

            return result;
        }

        public static bool ExecuteReader(string query)
        {
            bool result = false;
            SqlConnection con = new SqlConnection(ConnectionString);
            SqlDataAdapter da = new SqlDataAdapter();

            try
            {
                con.Open();
                da.SelectCommand = new SqlCommand(query, con);
                con.Close();
                dt = new DataTable();
                da.Fill(dt);

                if (dt.Rows.Count == 1 && dt.Columns.Count == 1)
                {
                    if (dt.Rows[0][0].ToString() == "true")
                    {
                        result = true;
                    }
                    else
                    {
                        result = false;
                    }
                }
            } catch (Exception)
            {
                result = false;
            }

            return result;
        }
    }
}

当我这样查询时

query = "insert into client(account_id, name, receive_email) values(" + accountId + ", '" + clientBLL.name + "', " + clientBLL.receiveMail + ");";

但是这种查询方法应该是非常糟糕的主意。好的方法是将要插入或检索的数据的参数传递给 SqlCommand。

像这样

query = @"insert into accounts(email, password, user_type) output inserted.id values(@email, @password, @userType);";
cmd.Parameters.Add("email", SqlDbType.NVarChar).Value = bll.email;
cmd.Parameters.Add("password", SqlDbType.VarBinary).Value = bll.password;
cmd.Parameters.Add("userType", SqlDbType.Bit).Value = 0;

但是我的DB Manager类不支持这个方法。我想要一个支持此 Sql 命令查询方法的 Db Manager 类，而不是旧的(我之前表达过)。我该怎么做。

Answer 1

显然，您需要将参数添加到您的 DBmanager 类中。它还缺少其他一些重要方法。这是您可以使用的完整类(class)。我在 web.config 中使用标准的 ConnectionStrings 部分，而不是 AppSettings 部分。您可以修改您的 web.config(推荐)，也可以修改此类。

//Author: Racil Hilan
//You are free to modify and use this class in any project, personal or commercial,
//as long as you include this note. The author assumes no responsibility whatsoever
//for any damage that results from using this class, and does not guarantee in any way
//the suitability of this class for any purpose.
using System;
using System.Configuration;
using System.Data;
using System.Data.Common;
using System.Data.SqlClient;

namespace DataLayer {
  /// <summary>Class that encapsulates a SQL Server database connection and CRUD operations.</summary>
  public class SQLServerDb : IDisposable {
    private DbConnection _con;

    /// <summary>Default constructor which uses the "DefaultConnection" connectionString.</summary>
    public SQLServerDb() : this("DefaultConnection") { }

    /// <summary>Constructor which takes the connection string name.</summary>
    /// <param name="connectionStringName"></param>
    public SQLServerDb(string connectionStringName) {
      string connectionString = ConfigurationManager.ConnectionStrings[connectionStringName].ConnectionString;
      _con = new SqlConnection(connectionString);
    }

    /// <summary>Executes a non-query command.</summary>
    /// <param name="command">The command to execute.</param>
    /// <returns>The count of records affected by the command.</returns>
    public int ExecuteNonQuery(DbCommand command) {
      int result = 0;
      if (command == null)
        throw new ArgumentException("Command cannot be null.");
      try {
        _con.Open();
        result = command.ExecuteNonQuery();
      }
      finally {
        _con.Close();
      }
      return result;
    }

    /// <summary>Executes a command that returns a single scalar value.</summary>
    /// <param name="command">The command to execute.</param>
    /// <returns>The value returned by executing the command.</returns>
    public object ExecuteScalar(DbCommand command) {
      object result = null;
      if (command == null)
        throw new ArgumentException("Command cannot be null.");
      try {
        _con.Open();
        result = command.ExecuteScalar();
      }
      finally {
        _con.Close();
      }
      return result;
    }

    /// <summary>Executes a command that returns a DataSet.</summary>
    /// <param name="command">The command to execute.</param>
    /// <returns>The DataSet returned by executing the ecommand.</returns>
    public DataSet ExecuteDataSet(DbCommand command) {
      DataSet ds = new DataSet();
      if (command == null)
        throw new ArgumentException("Command cannot be null.");
      try {
        DbDataAdapter ad = new SqlDataAdapter((SqlCommand)command);
        ad.Fill(ds);
      }
      finally {
        _con.Close();
      }
      return ds;
    }

    /// <summary>Creates a command with the given parameters.</summary>
    /// <param name="commandText">The SQL query to execute.</param>
    /// <returns>The created command.</returns>
    public DbCommand GetSqlStringCommand(string commandText) {
      return GetCommand(commandText, CommandType.Text);
    }

    /// <summary>Creates a command with the given parameters.</summary>
    /// <param name="commandText">The name of the stored procedure to execute.</param>
    /// <returns>The created command.</returns>
    public DbCommand GetStoredProcedureCommand(string commandText) {
      return GetCommand(commandText, CommandType.StoredProcedure);
    }

    /// <summary>Creates a command with the given parameters.</summary>
    /// <param name="commandText">The name of the stored procedure to execute.</param>
    /// <returns>The created command.</returns>
    private DbCommand GetCommand(string commandText, CommandType commandType) {
      DbCommand command = _con.CreateCommand();
      command.CommandType = commandType;
      command.CommandText = commandText;
      return command;
    }

    /// <summary>Adds an in parameter to a command.</summary>
    /// <param name="command">The SQL query to execute</param>
    /// <param name="name">The name of the parameter.</param>
    /// <param name="dbType">The type of the parameter.</param>
    /// <param name="value">The value of the parameter.</param>
    public void AddInParameter(DbCommand command, string name, DbType dbType, object value) {
      AddParameter(command, name, dbType, value, ParameterDirection.Input, 0);
    }

    /// <summary>Adds an out parameter to a command.</summary>
    /// <param name="command">The SQL query to execute</param>
    /// <param name="name">The name of the parameter.</param>
    /// <param name="dbType">The type of the parameter.</param>
    /// <param name="size">The maximum size, in bytes, of the data within the column.</param>
    public void AddOutParameter(DbCommand command, string name, DbType dbType, int size) {
      AddParameter(command, name, dbType, null, ParameterDirection.Output, size);
    }

    /// <summary>Adds a parameter to a command.</summary>
    /// <param name="command">The SQL query to execute</param>
    /// <param name="name">The name of the parameter.</param>
    /// <param name="dbType">The type of the parameter.</param>
    /// <param name="value">The value of the parameter.</param>
    /// <param name="direction">The direction for the parameter.</param>
    /// <param name="size">The maximum size, in bytes, of the data within the column.</param>
    private void AddParameter(DbCommand command, string name, DbType dbType, object value, ParameterDirection direction, int size) {
      var parameter = command.CreateParameter();
      parameter.ParameterName = name;
      parameter.DbType = dbType;
      parameter.Value = value ?? DBNull.Value;
      parameter.Direction = direction;
      if (size > 0)
        parameter.Size = size;
      command.Parameters.Add(parameter);
    }

    public void Dispose() {
      if (_con != null) {
        _con.Dispose();
        _con = null;
      }
    }
  }
}

您可以像这样在示例中使用它:

var db = new SQLServerDb();
string sql = @"INSERT INTO accounts(email, password, user_type) VALUES(@email, @password, @userType);";
DbCommand cmd = db.GetSqlStringCommand(sql);
db.AddInParameter(cmd, "@email", DbType.String, bll.email);
db.AddInParameter(cmd, "@password", DbType.String, bll.password);
db.AddInParameter(cmd, "@userType", DbType.Boolean, bll.userType);
DataRow dr = db.ExecuteDataSet(cmd).Tables[0].Rows[0];

要将其用于存储过程而非查询，请使用 GetStoredProcedureCommand() 而不是 GetSqlStringCommand()。