C# 操作PostgreSQL 数据库的示例代码

操作类

/// <summary>
  /// 数据库操作基类(for PostgreSQL)
  /// </summary>
  public class PostgreHelper : IDBHelper
  {
    /// <summary>
    /// 得到数据条数
    /// </summary>
    public int GetCount(string connectionString, string tblName, string condition)
    {
      StringBuilder sql = new StringBuilder("select count(*) from " + tblName);
      if (!string.IsNullOrEmpty(condition))
        sql.Append(" where " + condition);

      object count = ExecuteScalar(connectionString, CommandType.Text, sql.ToString(), null);
      return int.Parse(count.ToString());
    }

    /// <summary>
    /// 执行查询，返回DataSet
    /// </summary>
    public DataSet ExecuteQuery(string connectionString, CommandType cmdType, string cmdText,
      params DbParameter[] cmdParms)
    {
      using (NpgsqlConnection conn = new NpgsqlConnection(connectionString))
      {
        using (NpgsqlCommand cmd = new NpgsqlCommand())
        {
          PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
          using (NpgsqlDataAdapter da = new NpgsqlDataAdapter(cmd))
          {
            DataSet ds = new DataSet();
            da.Fill(ds, "ds");
            cmd.Parameters.Clear();
            return ds;
          }
        }
      }
    }

    /// <summary>
    /// 在事务中执行查询，返回DataSet
    /// </summary>
    public DataSet ExecuteQuery(DbTransaction trans, CommandType cmdType, string cmdText,
      params DbParameter[] cmdParms)
    {
      NpgsqlCommand cmd = new NpgsqlCommand();
      PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, cmdParms);
      NpgsqlDataAdapter da = new NpgsqlDataAdapter(cmd);
      DataSet ds = new DataSet();
      da.Fill(ds, "ds");
      cmd.Parameters.Clear();
      return ds;
    }

    /// <summary>
    /// 执行 Transact-SQL 语句并返回受影响的行数。
    /// </summary>
    public int ExecuteNonQuery(string connectionString, CommandType cmdType, string cmdText,
      params DbParameter[] cmdParms)
    {
      NpgsqlCommand cmd = new NpgsqlCommand();

      using (NpgsqlConnection conn = new NpgsqlConnection(connectionString))
      {
        PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
        int val = cmd.ExecuteNonQuery();
        cmd.Parameters.Clear();
        return val;
      }
    }

    /// <summary>
    /// 在事务中执行 Transact-SQL 语句并返回受影响的行数。
    /// </summary>
    public int ExecuteNonQuery(DbTransaction trans, CommandType cmdType, string cmdText,
      params DbParameter[] cmdParms)
    {
      NpgsqlCommand cmd = new NpgsqlCommand();
      PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, cmdParms);
      int val = cmd.ExecuteNonQuery();
      cmd.Parameters.Clear();
      return val;
    }

    /// <summary>
    /// 执行查询，返回DataReader
    /// </summary>
    public DbDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText,
      params DbParameter[] cmdParms)
    {
      NpgsqlCommand cmd = new NpgsqlCommand();
      NpgsqlConnection conn = new NpgsqlConnection(connectionString);

      try
      {
        PrepareCommand(cmd, conn, null, cmdType, cmdText, cmdParms);
        NpgsqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
        cmd.Parameters.Clear();
        return rdr;
      }
      catch
      {
        conn.Close();
        throw;
      }
    }

    /// <summary>
    /// 在事务中执行查询，返回DataReader
    /// </summary>
    public DbDataReader ExecuteReader(DbTransaction trans, CommandType cmdType, string cmdText,
      params DbParameter[] cmdParms)
    {
      NpgsqlCommand cmd = new NpgsqlCommand();
      PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, cmdParms);
      NpgsqlDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
      cmd.Parameters.Clear();
      return rdr;
    }

    /// <summary>
    /// 执行查询，并返回查询所返回的结果集中第一行的第一列。忽略其他列或行。
    /// </summary>
    public object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText,
      params DbParameter[] cmdParms)
    {
      NpgsqlCommand cmd = new NpgsqlCommand();

      using (NpgsqlConnection connection = new NpgsqlConnection(connectionString))
      {
        PrepareCommand(cmd, connection, null, cmdType, cmdText, cmdParms);
        object val = cmd.ExecuteScalar();
        cmd.Parameters.Clear();
        return val;
      }
    }

    /// <summary>
    /// 在事务中执行查询，并返回查询所返回的结果集中第一行的第一列。忽略其他列或行。
    /// </summary>
    public object ExecuteScalar(DbTransaction trans, CommandType cmdType, string cmdText,
      params DbParameter[] cmdParms)
    {
      NpgsqlCommand cmd = new NpgsqlCommand();
      PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, cmdParms);
      object val = cmd.ExecuteScalar();
      cmd.Parameters.Clear();
      return val;
    }

    /// <summary>
    /// 生成要执行的命令
    /// </summary>
    /// <remarks>参数的格式：冒号+参数名</remarks>
    private static void PrepareCommand(DbCommand cmd, DbConnection conn, DbTransaction trans, CommandType cmdType,
      string cmdText, DbParameter[] cmdParms)
    {
      if (conn.State != ConnectionState.Open)
        conn.Open();

      cmd.Connection = conn;
      cmd.CommandText = cmdText.Replace("@", ":").Replace("?", ":").Replace("[", """).Replace("]", """);

      if (trans != null)
        cmd.Transaction = trans;

      cmd.CommandType = cmdType;

      if (cmdParms != null)
      {
        foreach (NpgsqlParameter parm in cmdParms)
        {
          parm.ParameterName = parm.ParameterName.Replace("@", ":").Replace("?",":");

          cmd.Parameters.Add(parm);
        }
      }
    }
  }

								 
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