public static Expression AsConstantExpression(this object value, bool parameterised = false)
{
if (!parameterised)
{
return(Expression.Constant(value));
}
var valueType = value.GetType();
var makeTuple =
ExpressionEx.Converter(typeof(object), v =>
typeof(Expression).Call("Constant", new Type[] { }, typeof(Tuple).Call("Create", new[] { valueType }, v.CastAs(valueType)))
)
.Compile()
.AsConstantExpression();
var makeConstantExpression =
ExpressionEx.Converter(typeof(object), v =>
typeof(Expression).Call("Property", new Type[] { }, Expression.Invoke(makeTuple, v), "Item1".AsConstantExpression())
)
.Compile();
var res = ((Func <object, MemberExpression>)makeConstantExpression)(value);
return((Expression)res);
}
public static IQueryable SelectMany(this IQueryable items, Func <ParameterExpression, Expression> projection)
{
var projectionLambda = ExpressionEx.Converter(items.ElementType, projection);
var queryableCallExpression = items.CallQueryable("SelectMany", new[] { items.ElementType, projectionLambda.ReturnType.GetEnumerableItemType() }, projectionLambda);
var projectedQuery = items.Transform(queryableCallExpression);
return(projectedQuery);
}
