使用Linq实现全外连接查询

  var Query = dtNewPO.AsEnumerable().AsQueryable().FullOuterJoin(dtOldPO.AsEnumerable().AsQueryable(),
                       p => p.Field<string>("MaterielID") + p.Field<int>("SalesOrderDetailID"),
                       c => c.Field<string>("MaterielID") + c.Field<int>("SalesOrderDetailID"));

 FullOuterJoin：注意重写了该方法具体内容如下：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Linq.Expressions;

/// <summary>
///LinqFullOuterJoin 的摘要说明 For Linq FullOuterJoin Query
/// </summary>

public class Duple<T1, T2>
{

    public T1 Element1
    {
        get;
        set;
    }

    public T2 Element2
    {
        get;
        set;
    }

}

public static class MyQueryable
{
    public static IQueryable<Duple<TOuter, TInner>> FullOuterJoin<TOuter, TInner, TKey>(this IQueryable<TOuter> outer, IQueryable<TInner> inner,
        Expression<Func<TOuter, TKey>> outerKeySelector, Expression<Func<TInner, TKey>> innerKeySelector)

        where TOuter : class

        where TInner : class
    {

        return outer.Join(inner, outerKeySelector, innerKeySelector, (o, i) => new Duple<TOuter, TInner>
        {
            Element1 = o,
            Element2 = i
        })

            .Concat(LeftAntiSemiJoin(outer, inner, outerKeySelector, innerKeySelector).Select(o => new Duple<TOuter, TInner>
            {
                Element1 = o,
                Element2 = null
            }))

            .Concat(LeftAntiSemiJoin(inner, outer, innerKeySelector, outerKeySelector).Select(i => new Duple<TOuter, TInner>
            {
                Element1 = null,
                Element2 = i
            }));

    }



    public static IQueryable<TOuter> LeftAntiSemiJoin<TOuter, TInner, TKey>(

        this IQueryable<TOuter> outer,

        IQueryable<TInner> inner,

        Expression<Func<TOuter, TKey>> outerKeySelector,

        Expression<Func<TInner, TKey>> innerKeySelector)
    {

        return outer

            .GroupJoin(inner, outerKeySelector, innerKeySelector, (o, i) => new
            {
                Outer = o,
                Group = i
            })

            .Where(r => !r.Group.Any())

            .Select(r => r.Outer);

    }

}