protected override Expression VisitMethodCall(MethodCallExpression node)
{
if (node.Method.Name == "Select")
{
if (node.Arguments[0].ToString().StartsWith(ProjectToParameterName)) //this is a Select created by Project.To().
{
//Apply relevant filters.
var newArg0 = ApplyFilters(node.Arguments[0]);
//pass the second argument to a new query visitor to visit the remainder of the tree recursively & return the result
QueryInjectorExpressionVisitor inner = new QueryInjectorExpressionVisitor();
inner._expressions = _expressions;
inner._rootFilters = _rootFilters;
inner._pathSoFar = _pathSoFar + node.Arguments[0].ToString().Replace(ProjectToParameterName, string.Empty) + ".";
var newArg1 = inner.Visit(node.Arguments[1]);
//Construct a new call to Select using the new args & return it
return(Expression.Call(null, node.Method, newArg0, newArg1));
}
}
return(base.VisitMethodCall(node));
}
private void AddrelatedEntityFiltersIfApplicable <T>(Dictionary <Expression, Expression> relatedEntityFilters, Lictionary <Type, PropertyInfo> usingRelationships, ref IQueryable <T> query)
{
var filters = relatedEntityFilters.Clone();
var rootFilters = new Dictionary <Type, Expression>();
var props = this.GetType().GetProperties().Where(x =>
x.PropertyType.GetGenericTypeDefinition() == typeof(ISetAccessor) ||
typeof(ISetAccessor).IsAssignableFrom(x.PropertyType));
//group the properties by entity type, & exclude any type for which accessors are explicitly specified in a .Using() call
var groupedProps = props.GroupBy(x => x.PropertyType.GetGenericArguments()[1]).Where(x => !usingRelationships.ContainsKey(x.Key)).ToDictionary(x => x.Key, x => x.Select(i => i).ToList());
//Add the filters specified in .Using() calls
foreach (var key in usingRelationships.Keys)
{
if (usingRelationships[key].Count == 1)
{
var prop = usingRelationships[key].Single();
var setAccessor = prop.GetValue(this);
var filter = (Expression)typeof(ISetAccessor).GetProperty("FilterExpression").GetValue(setAccessor);
if (filter != null && filter.NodeType == ExpressionType.Lambda)
{
if ((filter as LambdaExpression).Body != (filter as LambdaExpression).Parameters[0])
{ //filter expression actually does something so use it.
var entityType = prop.PropertyType.GetGenericArguments()[1];
rootFilters.Add(entityType, filter);
}
}
}
else if (usingRelationships[key].Count > 1)
{
throw new CatFlapException("Only one .Using() can be specified per entity type per data retrieval operation. Multiple usings specified for: " + key.FullName);
}
else
{
throw new CatFlapException("usingRelationships collection cannot be empty");
}
}
foreach (var group in groupedProps)
{
PropertyInfo prop = null;
if (group.Value.Count() == 1)
{
prop = group.Value.Single();
}
else if (group.Value.Count() > 1)
{
var multiple = group.Value.Count(x => x.GetCustomAttributes <DefaultAttribute>().Count() == 1) > 1;
if (multiple)
{
throw new CatFlapSetAccessorException("Ambiguous choice for relationship collection filter.\r\nMore than one SetAccessor<" + this.GetType().BaseType.GetGenericArguments()[0].FullName + "," + group.Key.FullName + "> property of " + this.GetType().FullName + " is decorated with the [RelationshipFilter] attribute.");
}
var none = group.Value.Count(x => x.GetCustomAttributes <DefaultAttribute>().Count() == 1) == 0;
if (none)
{
throw new CatFlapSetAccessorException("Ambiguous choice for relationship collection filter.\r\nMore than one SetAccessor<" + this.GetType().BaseType.GetGenericArguments()[0].FullName + "," + group.Key.FullName + "> property exists on " + this.GetType().FullName + " but none is decorated with the [RelationshipFilter] attribute.");
}
prop = group.Value.Single(x => x.GetCustomAttributes <DefaultAttribute>().Count() == 1);
}
if (prop != null)
{
var setAccessor = prop.GetValue(this);
var filter = (Expression)typeof(ISetAccessor).GetProperty("FilterExpression").GetValue(setAccessor);
if (filter != null && filter.NodeType == ExpressionType.Lambda)
{
if ((filter as LambdaExpression).Body != (filter as LambdaExpression).Parameters[0])
{ //filter expression actually does something so use it.
var entityType = group.Key;
rootFilters.Add(entityType, filter);
}
}
}
}
if (filters.Count > 0 || rootFilters.Count > 0)
{
//inject the navigation property filters
var resultingExpression = new QueryInjectorExpressionVisitor(filters, rootFilters).Visit((query as IQueryable).Expression);
query = query.Provider.CreateQuery <T>(resultingExpression);
}
}
