我有你需要的源代码 - 但不知道如何附加文件。
这里有一些sn-ps（sn-ps！我不得不修改这段代码，所以它可能无法编译）：
可查询：
public class QueryTranslator<T> : IOrderedQueryable<T>
{
private Expression _expression = null;
private QueryTranslatorProvider<T> _provider = null;
public QueryTranslator(IQueryable source)
{
_expression = Expression.Constant(this);
_provider = new QueryTranslatorProvider<T>(source);
}
public QueryTranslator(IQueryable source, Expression e)
{
if (e == null) throw new ArgumentNullException("e");
_expression = e;
_provider = new QueryTranslatorProvider<T>(source);
}
public IEnumerator<T> GetEnumerator()
{
return ((IEnumerable<T>)_provider.ExecuteEnumerable(this._expression)).GetEnumerator();
}
IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return _provider.ExecuteEnumerable(this._expression).GetEnumerator();
}
public Type ElementType
{
get { return typeof(T); }
}
public Expression Expression
{
get { return _expression; }
}
public IQueryProvider Provider
{
get { return _provider; }
}
}
IQueryProvider：
public class QueryTranslatorProvider<T> : ExpressionTreeTranslator, IQueryProvider
{
IQueryable _source;
public QueryTranslatorProvider(IQueryable source)
{
if (source == null) throw new ArgumentNullException("source");
_source = source;
}
#region IQueryProvider Members
public IQueryable<TElement> CreateQuery<TElement>(Expression expression)
{
if (expression == null) throw new ArgumentNullException("expression");
return new QueryTranslator<TElement>(_source, expression) as IQueryable<TElement>;
}
public IQueryable CreateQuery(Expression expression)
{
if (expression == null) throw new ArgumentNullException("expression");
Type elementType = expression.Type.FindElementTypes().First();
IQueryable result = (IQueryable)Activator.CreateInstance(typeof(QueryTranslator<>).MakeGenericType(elementType),
new object[] { _source, expression });
return result;
}
public TResult Execute<TResult>(Expression expression)
{
if (expression == null) throw new ArgumentNullException("expression");
object result = (this as IQueryProvider).Execute(expression);
return (TResult)result;
}
public object Execute(Expression expression)
{
if (expression == null) throw new ArgumentNullException("expression");
Expression translated = this.Visit(expression);
return _source.Provider.Execute(translated);
}
internal IEnumerable ExecuteEnumerable(Expression expression)
{
if (expression == null) throw new ArgumentNullException("expression");
Expression translated = this.Visit(expression);
return _source.Provider.CreateQuery(translated);
}
#endregion
#region Visits
protected override MethodCallExpression VisitMethodCall(MethodCallExpression m)
{
return m;
}
protected override Expression VisitUnary(UnaryExpression u)
{
return Expression.MakeUnary(u.NodeType, base.Visit(u.Operand), u.Type.ToImplementationType(), u.Method);
}
#endregion
}
用法（警告：改编代码！可能无法编译）：
private Dictionary<Type, object> _table = new Dictionary<Type, object>();
public override IQueryable<T> GetObjectQuery<T>()
{
if (!_table.ContainsKey(type))
{
_table[type] = new QueryTranslator<T>(
_ctx.CreateQuery<T>("[" + typeof(T).Name + "]"));
}
return (IQueryable<T>)_table[type];
}
表达访问者/翻译者：
http://blogs.msdn.com/mattwar/archive/2007/07/31/linq-building-an-iqueryable-provider-part-ii.aspx
http://msdn.microsoft.com/en-us/library/bb882521.aspx
编辑：添加 FindElementTypes()。希望现在所有方法都存在。
/// <summary>
/// Finds all implemented IEnumerables of the given Type
/// </summary>
public static IQueryable<Type> FindIEnumerables(this Type seqType)
{
if (seqType == null || seqType == typeof(object) || seqType == typeof(string))
return new Type[] { }.AsQueryable();
if (seqType.IsArray || seqType == typeof(IEnumerable))
return new Type[] { typeof(IEnumerable) }.AsQueryable();
if (seqType.IsGenericType && seqType.GetGenericArguments().Length == 1 && seqType.GetGenericTypeDefinition() == typeof(IEnumerable<>))
{
return new Type[] { seqType, typeof(IEnumerable) }.AsQueryable();
}
var result = new List<Type>();
foreach (var iface in (seqType.GetInterfaces() ?? new Type[] { }))
{
result.AddRange(FindIEnumerables(iface));
}
return FindIEnumerables(seqType.BaseType).Union(result);
}
/// <summary>
/// Finds all element types provided by a specified sequence type.
/// "Element types" are T for IEnumerable<T> and object for IEnumerable.
/// </summary>
public static IQueryable<Type> FindElementTypes(this Type seqType)
{
return seqType.FindIEnumerables().Select(t => t.IsGenericType ? t.GetGenericArguments().Single() : typeof(object));
}