如何从数据库动态设置值

Question

My search queries will always return one row and put it into a datatable.

Is there a way that I can check if the column name and the property name matches, then set the value?

For example:

    SELECT * FROM mytable WHERE ID = 10;

Query returns column names: "ID, ScriptName, Type, Flags, VerifiedBuild" and their values.

Then run a foreach statement checking if the column name and property name match and set the property values below.

    public int ID { get; set; }
    public int ScriptName { get; set; }
    public int Type { get; set; }
    public int Flags { get; set; }
    public int VerifiedBuild { get; set; }

Answer 1

You can do it very easly using EntityLite , at its core, EntityLite can materialize entities from data readers. This funtionallity is publically exposed.

Imagine you have a method like the following;

public IDataReader GetDataReaderFromQuery()
{
    //TODO: implement this method
    throw new NotImplementedException();
}

And one POCO entity:

public class MyEntity 
{
    // properties go here
}

you can use FisrtOrDefault, ToEnumberable and ToList extension methods on the datareader to get POCO entities:

using inercya.EntityLite;
using inercya.EntityLite.Extensions;

//......

MyEntity SomeMethod()
{
    using (reader = GetDataReaderFromQuery())
    {

         return reader.FirstOrDefault<MyEntity>();
    }
}

EntityLite will build a method at runtime using DynamicMethod that materializes an entity of that type from that specific datareader. The method is cached, so if you need to materialize more entities of that type from datareaders with the same schema, the method is reused. It is almost as fast as de best handwritten code.

Answer 2

With the help of FastDynamic (a tiny library that helps you to efficiently create objects and to access properties of compile-time-unkonwn types), you could write the following data reader extension methods:

using FastDynamic;
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Sample
{
    public static class DataReaderExtensions
    {
        private static void SetPropertiesFromDataReader(IDataReader reader, object entity)
        {
            if (reader == null || entity == null) throw new ArgumentNullException();
            Type entityType = entity.GetType();
            var setters = entityType.GetSetters();
            for (int fieldIndex = 0; fieldIndex < reader.FieldCount; fieldIndex++)
            {
                var fieldName = reader.GetName(fieldIndex);
                Setter setter = null;
                if (!string.IsNullOrEmpty(fieldName) && setters.TryGetValue(fieldName, out setter))
                {
                    if (!reader.IsDBNull(fieldIndex))
                    {
                        setter(entity, reader.GetValue(i));
                    }
                }
            }
        }

        public static IEnumerable<T> ToEnumberable<T>(this IDataReader reader) where T:class, new()
        {
            Type entityType = typeof(T);
            Func<object> activator = entityType.GetActivator();
            while (reader.Read())
            {
                var entity = activator();
                SetPropertiesFromDataReader(reader, entity);
                yield return (T)entity;
            }
        }

        public T FirstOrDefault<T>(this IDataReader reader) where T : class, new()
        {
            return reader.ToEnumberable<T>().FirstOrDefault();
        }

        public List<T> ToList<T>(this IDataReader reader) where T : class, new()
        {
            return reader.ToEnumberable<T>().ToList();
        }

    }
}

Answer 3

Yes. You need to use reflection. By using reflection you can get parameter names in an array and you can compare names in a for loop.

ParameterInfo