private LambdaExpression Parameterize(Expression query, out object[] arguments)
{
IQueryProvider provider = this.FindProvider(query);
if (provider == null)
{
throw new ArgumentException(Res.ArgumentQuery);
}
var ep = provider as IDbContext;
// turn all relatively constant expression into actual constants
Func <Expression, bool> fnCanBeEvaluated = e => ep != null?ExpressionHelper.CanBeEvaluatedLocally(e) : true;
var body = PartialEvaluator.Eval(query, fnCanBeEvaluated);
// convert all constants into parameters
List <ParameterExpression> parameters;
List <object> values;
body = Parameterizer.Parameterize(body, out parameters, out values);
// make sure the body will return a value typed as 'object'.
if (body.Type != typeof(object))
{
body = Expression.Convert(body, typeof(object));
}
// make a lambda expression with these parameters
arguments = values.ToArray();
if (arguments.Length < 5)
{
return(Expression.Lambda(body, parameters.ToArray()));
}
else
{
// too many parameters, use an object array instead.
arguments = new object[] { arguments };
return(ExplicitToObjectArray.Rewrite(body, parameters));
}
}
