public object Execute(Expression expression)
{
object source = null;
if (expression.NodeType == ExpressionType.Call)
{
expression = new SourceReplacement().Visit(expression);
Debug.Assert(expression.NodeType == ExpressionType.Call);
var method = ((MethodCallExpression)expression).Method;
//Debug.Assert(method.IsGenericMethod);
var args = ((MethodCallExpression)expression).Arguments.Select(o => ExpressionCalculater.Eval(o, null)).ToArray();
source = method.Invoke(null, args);
}
else
{
source = ExpressionCalculater.Eval(expression);
if (source is IQueryable)
{
var type = source.GetType();
Debug.Assert(type.IsGenericType);
Debug.Assert(type.GetGenericArguments().Length == 1);
var t = typeof(List <>).MakeGenericType(source.GetType().GetGenericArguments()[0]);
var list = (IList)Activator.CreateInstance(t);
foreach (var item in (IQueryable)source)
{
list.Add(item);
}
source = list;
}
}
return(source);
}
private void VisitNegate(UnaryExpression node)
{
var value = ExpressionCalculater.Eval(node.Operand, null);
value = Arithmetic.Negate(value, node.Type);
PushValue(value);
}
static Func <T, TResult> CreateFunc1 <T, TResult>(LambdaExpression lamb)
{
Debug.Assert(lamb.Parameters.Count == 1);
Func <T, TResult> f = delegate(T arg)
{
var p = new ObjectParameter(lamb.Parameters[0].Name, arg);
var result = ExpressionCalculater.Eval(lamb.Body, p);
return((TResult)result);
};
return(f);
}
static Func <T1, T2, TResult> CreateFunc2 <T1, T2, TResult>(LambdaExpression lamb)
{
Debug.Assert(lamb.Parameters.Count == 2);
Func <T1, T2, TResult> f = delegate(T1 arg0, T2 arg1)
{
var p0 = new ObjectParameter(lamb.Parameters[0].Name, arg0);
var p1 = new ObjectParameter(lamb.Parameters[1].Name, arg1);
var result = ExpressionCalculater.Eval(lamb.Body, p0, p1);
return((TResult)result);
};
return(f);
}
protected override Expression VisitMemberAccess(MemberExpression m)
{
if (typeof(IQueryable).IsAssignableFrom(m.Type))
{
Debug.Assert(m.Expression.NodeType == ExpressionType.Constant);
this.queryProvider = (IQueryProvider)ExpressionCalculater.Eval(m);
}
if (this.queryProvider != null)
{
return(m);
}
return(base.VisitMemberAccess(m));
}
