如何在SqlDataReader中使用Generic

Question

我试图想出一种方法,只是将SQL Server中的表加载到一个类中,而不必告诉它任何东西.基本上,只需创建类并让它知道要加载什么,基于此.这是我到目前为止所拥有的.

我的问题是,是否有一些方法可以避免硬编码类型,调用reader.readString,reader.readInt32等.基于FieldType？

 private Int32? readInt32(SqlDataReader reader, string columnName)
    {
        Int32? result = null;


        if (!reader.IsDBNull(reader.GetOrdinal(columnName)))
        {
            result = reader.GetInt32(reader.GetOrdinal(columnName));
        };

        return result;
    }

  public List<T> readTable(string table, string wherecls, string connStr)
    {
        List<T> result = new List<T>();
        using (SqlConnection connection = new SqlConnection(connStr))
        {
            using (SqlCommand command = connection.CreateCommand())
            {
                command.CommandText = "select * from " + table;
                if (wherecls.Length > 0) command.CommandText += " where " + wherecls;
                connection.Open();
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        Object i = Activator.CreateInstance(typeof(T));

                        System.Reflection.FieldInfo[] fieldInfoList = typeof(T).GetFields();
                        foreach (System.Reflection.FieldInfo f in fieldInfoList)
                        {
                            if (f.FieldType == typeof(string)) f.SetValue(i, readString(reader, f.Name));
                            if (f.FieldType == typeof(Int32)) f.SetValue(i, readInt32(reader, f.Name));
                            if (f.FieldType == typeof(Int16)) f.SetValue(i, readInt16(reader, f.Name));
                            if (f.FieldType == typeof(byte)) f.SetValue(i, readByte(reader, f.Name));
                            if (f.FieldType == typeof(short)) f.SetValue(i, readShort(reader, f.Name));
                        }
                        result.Add((T)i);
                    }
                }
            }
        }
        return result;
    }

谢谢Dan Chase

Answer 1

你所描述的是很多工作......而且正是像"小精灵" 这样的工具已经做了.所以我的建议在这里:使用小巧玲珑:

// Dapper adds a Query<T>(this DbConnection, ...) extension method
var data = connection.Query<T>(sql, args).AsList();

但是,我会说让string wherecls我的脊椎发抖 - 这听起来像是一个SQL注入的噩梦.但是......这取决于你.