protected override Expression VisitMember(MemberExpression node)
{
Expression result = null;
if (node.Expression != null && node.Expression.Type == typeof(TFrom))
{
Expression expression = this.Visit(node.Expression);
if (expression.Type != typeof(TTo))
{
throw new Exception("An error occurred");
}
LambdaExpression lambdaExpression;
if (this.Mappings.TryGetValue(node.Member, out lambdaExpression))
{
Expression param = lambdaExpression.Parameters.Single();
result = new FlexVisitor(
(expr) => expr == param,
(expr) => expression
).Visit(lambdaExpression.Body);
}
else
{
result = Expression.Property(expression, node.Member.Name);
}
}
else
{
result = base.VisitMember(node);
}
return(result);
}
public TResult Execute <TResult>(System.Linq.Expressions.Expression expression)
{
if (this.Transform == null)
{
throw new InvalidOperationException("Must specify a transform before performing a query against the TransformQueryProvider");
}
if (!this.Visitor.ConstantMappings.ContainsKey(this.ConstantExpression))
{
this.Visitor.ConstantMappings.Add(this.ConstantExpression, this.InnerQueryable.Expression);
}
TResult result = default(TResult);
TypeInfo qType = typeof(IQueryable).GetTypeInfo();
Type gqType = typeof(IQueryable <>);
TypeInfo gqTypeInfo = gqType.GetTypeInfo();
Type resType = typeof(TResult);
TypeInfo resTypeInfo = resType.GetTypeInfo();
// Check if the type being requested can accept an IQueryable<T>, in which case we should not evaluate the expression
// but instead return a new query. First check is to ensure the TResult type is an interface, otherwise the rest definitely
// won't work, so returning null to short-circuit the logic. Seems like the best way to do it for performance and compactness,
// so lots of reflection operations don't needlessly occur.
var query = !resTypeInfo.IsInterface
? null
: (new TypeInfo[] { resTypeInfo })
.Union(resTypeInfo.GetInterfaces().Select(i => i.GetTypeInfo()))
.Where(i => i.IsGenericType &&
qType.IsAssignableFrom(i) &&
i.GetGenericTypeDefinition() == gqType)
.SingleOrDefault();
if (query != null)
{
result = DynamicallyCreateQuery <TResult>(query.GetGenericArguments()[0], expression);
//result = (TResult)this
// .CallMethod(
// new Type[] {
// query.GetGenericArguments()[0]
// },
// "CreateQuery",
// expression);
}
else if (resType == typeof(IEnumerable <TTo>))
{
expression = this.Visitor.Visit(expression);
FlexVisitor vis = new FlexVisitor((exp) => exp == this.ConstantExpression, (exp) => this.InnerQueryable.Expression);
expression = vis.Visit(expression);
var temp = InnerQueryable.Provider.CreateQuery <TFrom>(expression).ToArray();
if (this.Transform != null)
{
result = (TResult)((object)temp.Select(o => Transform(o)));
}
}
else if (resType == typeof(TTo))
{
expression = this.Visitor.Visit(expression);
FlexVisitor vis = new FlexVisitor((exp) => exp == this.ConstantExpression, (exp) => this.InnerQueryable.Expression);
expression = vis.Visit(expression);
var temp = InnerQueryable.Provider.Execute <TFrom>(expression);
if (this.Transform != null)
{
result = (TResult)((object)Transform(temp));
}
}
else
{
expression = this.Visitor.Visit(expression);
FlexVisitor vis = new FlexVisitor((exp) => exp == this.ConstantExpression, (exp) => this.InnerQueryable.Expression);
expression = vis.Visit(expression);
result = InnerQueryable.Provider.Execute <TResult>(expression);
}
return(result);
}
