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LINQ select all items of all subcollections that contain a string

I'm using jqueryui autocomplete to assist user in an item selection. I'm having trouble selecting the correct items from the objects' subcollections.
Object structure (simplified) is
public class TargetType
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<SubCategory> SubCategories { get; set; }
public TargetType()
{
SubCategories = new HashSet<SubCategory>();
}
}
public class SubCategory
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<SubTargetType> SubTargetTypes { get; set; }
public SubCategory()
{
SubTargetTypes = new HashSet<SubTargetType>();
}
}
Currently I'm doing this with nested foreach loops, but is there a better way?
Current code:
List<SubTargetResponse> result = new List<SubTargetResponse>();
foreach (SubCategory sc in myTargetType.SubCategories)
{
foreach (SubTargetType stt in sc.SubTargetTypes)
{
if (stt.Name.ToLower().Contains(type.ToLower()))
{
result.Add(new SubTargetResponse {
Id = stt.Id,
CategoryId = sc.Id,
Name = stt.Name });
}
}
}

You can do using Linq like this
var result = myTargetType.SubCategories
.SelectMany(sc => sc.SubTargetTypes)
.Where(stt => stt.Name.ToLower().Contains(type.ToLower()))
.Select(stt => new SubTargetResponse {
Id = stt.Id,
CategoryId = sc.Id,
Name = stt.Name });
The above query doesn't work. The following should work, but I'd not recommend that as that'd not be faster or more readable.
var result = myTargetType.SubCategories
.Select(sc => new Tuple<int, IEnumerable<SubTargetType>>
(sc.Id,
sc.SubTargetTypes.Where(stt => stt.Name.ToLower().Contains(type.ToLower()))))
.SelectMany(tpl => tpl.Item2.Select(stt => new SubTargetResponse {
Id = stt.Id,
CategoryId = tpl.Item1,
Name = stt.Name }));

Actually there are 2 different questions.
LINQ select all items of all subcollections that contain a string
Solutions:
(A) LINQ syntax:
var result =
(from sc in myTargetType.SubCategories
from stt in sc.SubTargetTypes.Where(t => t.Name.ToLower().Contains(type.ToLower()))
select new SubTargetResponse
{
Id = stt.Id,
CategoryId = sc.Id,
Name = stt.Name
})
.ToList();
(B) Method syntax:
var result =
myTargetType.SubCategories.SelectMany(
sc => sc.SubTargetTypes.Where(stt => stt.Name.ToLower().Contains(type.ToLower())),
(sc, stt) => new SubTargetResponse
{
Id = stt.Id,
CategoryId = sc.Id,
Name = stt.Name
})
.ToList();
Currently I'm doing this with nested foreach loops, but is there a better way?
Well, it depends of what do you mean by "better". Compare your code with LINQ solutions and answer the question. I personally do not see LINQ being better in this case (except no curly braces and different indentation, but a lot of a hidden garbage), and what to say about the second LINQ version in this answer - if that's "better" than your code, I don't know where are we going.

Group IEnumerable into a string

I wonder if someone could spare me a few minutes to give me some advice please?
I've created an IEnumerable list:
public class EmailBlock
{
public int alertCategory { get; set; }
public string alertName { get; set; }
public string alertURL { get; set; }
public string alertSnippet { get; set; } //Need to work out the snippet
}
List<EmailBlock> myEmailData = new List<EmailBlock>();
Which I then loop through some data (Umbraco content - not that that's really relevant!) and add items to the list.
myEmailData.Add(new EmailBlock { alertCategory = category.Id, alertName = alert.GetPropertyValue("pageTitle"), alertURL = alert.NiceUrl });
What ultimately I'd like to do is group the list by the alertCategory and then load each 'group' (another loop occurs later to check what members have subscribed to what alert category) into a variable which I can then use as an email's content.

You could use Linq's GroupBy() to do this:
using System.Linq
...
//Create a type to hold your grouped emails
public class GroupedEmail
{
public int AlertCategory { get; set; }
public IEnumerable<EmailBlock> EmailsInGroup {get; set; }
}
var grouped = myEmailData
.GroupBy(e => e.alertCategory)
.Select(g => new GroupedEmail
{
AlertCategory = g.Key,
EmailsInGroup = g
});
You can select to an anonymous type if required and project your sequence into whatever structure you require.

Linq has a nice group by statement:
var emailGroup = emailList.GroupBy(e => e.alertCategory);
Then you can loop through each grouping and do whatever you want:
foreach(var grouping in emailGroup)
{
//do whatever you want here.
//note grouping will access the list of grouped items, grouping.Key will show the grouped by field
}
Edit:
To retrieve a group after you have grouped them, just use Where for more than one or First for just one:
var group = emailGroup.First(g => g.Key == "name you are looking for");
or
var groups = emailGroup.Where(g => listOfWantedKeys.Contains(g.Key));
this is a lot more efficient than looping through every time you need to find something.

How can I select from an included entity in LINQ and get a flat list similar to a SQL Join would give?

I have two classes:
public class Topic
{
public Topic()
{
this.SubTopics = new HashSet<SubTopic>();
}
public int TopicId { get; set; }
public string Name { get; set; }
public virtual ICollection<SubTopic> SubTopics { get; set; }
}
public class SubTopic
public int SubTopicId { get; set; }
public int Number { get; set; }
public int TopicId { get; set; }
public string Name { get; set; }
public virtual Topic Topic { get; set; }
}
What I would like to do is to get a Data Transfer Object output from LINQ that will show me. I do want to see the TopicId repeated if there is more than one SubTopic inside that topic:
TopicId Name SubTopicId Name
1 Topic1 1 SubTopic1
1 Topic1 2 SubTopic2
1 Topic1 3 SubTopic3
2 Topic2 4 SubTopic4
I tried to code a Linq statement like this:
var r = context.Topics
.Select ( s => new {
id = s.TopicId,
name = s.Name,
sid = s.SubTopics.Select( st => st.SubTopicId),
sidname = s.SubTopics.Select ( st => st.Name)
}).
ToList();
But this does not really work as it returns sid and sidname as lists.
How will it be possible for me to get a flat output showing what I need?

You need SelectMany to expand a nested collection, along these lines
var r = context.Topics.SelectMany(t => t.SubTopics
.Select(st => new
{
TopicID = t.TopicId,
TopicName = t.Name,
SubTopicID = st.SubTopicId,
SubTopicName = st.Name
}));

try this :
var r = context.Topics
.Select ( s => new {
id = s.TopicId,
name = s.Name,
sid = s.SubTopics.Where(st=>st.TopicId==s.TopicId).Select( st => st.SubTopicId ),
sidname = s.SubTopics..Where(st=>st.TopicId==s.TopicId).Select ( st => st.Name)
}).
ToList();
Hope it will help

#Sweko provided an answer that satisfies the exact output that you requested. However, this can be even simpler if you just return the subtopic intact. It may run a bit quicker as well, since you don't need to create a new object for each element in the result.
Lastly, it looks like you wanted your result set ordered. For completeness, I've added those clauses as well.
var r = context.Topics
.SelectMany( topic => topic.SubTopics )
.OrderBy(sub => sub.TopicId)
.ThenBy(sub => sub.SubTopicId);

C# LINQ sub-where

I have object
public class OrderItem
{
public string idProduct { get; set; }
public int quantity { get; set; }
public List<WarehouseItem> WarehouseInfo = new List<WarehouseItem>();
}
public class WarehouseItem
{
public string Name{ get; set; }
public string LocnCode{ get; set; }
}
and i need select items which have WarehouseInfo.LocnCode == "A1"
It is doesnt work when I use something like
var items = itemList.Where(x => x.WarehouseInfo.Where(y => y.LocnCode.Equals("A1")));

Your requirements could be interpreted one of three ways, so here's three solutions:
Give me all OrderItems where ANY WarehouseItem has a LocnCode of "A1":
var items = itemList.Where(i => i.WarehouseInfo.Any(w => w.LocnCode == "A1"));
Give me all WarehouseItems within the OrderItems that have a LocnCode of "A1":
var items = itemList.SelectMany(i => i.WarehouseInfo)
.Where(w => w.LocnCode.Equals("A1"));
Give me all OrderItems where ANY WarehouseItem has a LocnCode of "A1", and filter WarehouseInfo to only those WarehouseItems:
This can't be done in a simple Linq query because there's no way to change the contents of the existing objects. You're going to have to create new objects with the filtered values:
var items = itemList.Where(i => i.WarehouseInfo.Any(w => w.LocnCode == "A1"))
.Select(i => new OrderItem
{
idProduct = i.idProduct,
quantity = i.quantity,
WarehouseInfo = i.WarehouseInfo.Where(w => w.LocnCode.Equals("A1"));
.ToList()
}
);

Try
var items = itemList.Where(x => x.WarehouseInfo.Any(y => y.LocnCode.Equals("A1")));
The Where takes a predicate that should return a bool. Any will return true if at least one item in the collection returns true for the given predicate.

Easiest way to merge two List<T>s

I've got two List<Name>s:
public class Name
{
public string NameText {get;set;}
public Gender Gender { get; set; }
}
public class Gender
{
public decimal MaleFrequency { get; set; }
public decimal MaleCumulativeFrequency { get; set; }
public decimal FemaleCumulativeFrequency { get; set; }
public decimal FemaleFrequency { get; set; }
}
If the NameText property matches, I'd like to take the FemaleFrequency and FemaleCumulativeFrequency from the list of female Names and the MaleFrequency and MaleCumulativeFrequency values from the list of male Names and create one list of Names with all four properties populated.
What's the easiest way to go about this in C# using .Net 3.5?

Are you attempting to sum each of the values when you merge the lists? If so, try something like this:
List<Name> list1 = new List<Name>();
List<Name> list2 = new List<Name>();
List<Name> result = list1.Union(list2).GroupBy(x => x.NameText).Select(x => new
Name
{
NameText = x.Key,
Gender = new Gender
{
FemaleCumulativeFrequency = x.Sum(y => y.Gender.FemaleCumulativeFrequency),
FemaleFrequency = x.Sum(y => y.Gender.FemaleFrequency),
MaleCumulativeFrequency = x.Sum(y => y.Gender.MaleCumulativeFrequency),
MaleFrequency = x.Sum(y => y.Gender.MaleFrequency)
}
}).ToList();
What this does is the following:
Unions the lists, creating an IEnumerable<Name> that contains the contents of both lists.
Groups the lists by the NameText property, so if there are duplicate Names with the same NameText, they'll show up in the same group.
Selects a set of new Name objects, with each grouped Name's properties summed... you can also use Average if that makes more sense.
Converts the entire query to a List<Name> by calling the "ToList()" method.
Edit: Or, as you've said below, you simply want to merge the two lists... do this:
List<Name> allNames = femaleNames.Union(maleNames).ToList();

This looks a lot like the census name frequency data, right? Gender is a bit of a misnomer for the class you have it's more like "FrequencyData".
In effect you want a Dictionary so you can lookup any name and get the four values for it. You could simply take the males and do ToDictionary(...) on it and then iterate over the females, if the name exists in the dictionary, replace the female probabilities on it, if it doesn't exist, create a new dictionary entry.
My own approach to this same data was to create a Table in a database with all four values attached.
Here's some code for your scenario ...
Dictionary<string, Gender> result;
result = males.ToDictionary(x => x.NameText, x => x.Gender);
foreach (var female in females)
{
if (result.ContainsKey(female.NameText))
{
result[female.NameText].FemaleCumulativeFrequency = female.Gender.FemaleCumulativeFrequency;
result[female.NameText].FemaleFrequency = female.Gender.FemaleFrequency;
}
else
result.Add(female.NameText, female.Gender);
}

I think this could be what you want although I'm not sure if it handles the cumulative frequencies as you'd expect:
var mergedNameList = maleNames
.Concat(femaleNames)
.GroupBy(n => n.NameText)
.Select(nameGroup => new Name
{
NameText = nameGroup.Key,
Gender = new Gender
{
MaleFrequency = nameGroup.Sum(n => n.Gender.MaleFrequency),
MaleCumulativeFrequency = nameGroup.Sum(n => n.Gender.MaleCumulativeFrequency),
FemaleFrequency = nameGroup.Sum(n => n.Gender.FemaleFrequency),
FemaleCumulativeFrequency = nameGroup.Sum(n => n.Gender.FemaleCumulativeFrequency)
}
}.ToList();