Merge three lists with linq

Question

I have three classes -

public class Type
{
   public int TypeId {get;set;}
   public string TypeName {get;set;}
}

public class SubType
{
   public int SubTypeId {get;set;}
   public string SubTypeName {get;set;}
}

public class Association
{
   public int TypeId {get;set;}
   public int SubTypeId {get;set;}
}

The Association gives the mapping between Type and SubType.

I have lists of each class - List<Type>, List<SubType>, List<Association>.

I want to merge them all into another like this - List<TypeInfo>. The TypeId and SubTypeId coming from the Assoication, the TypeName coming from Type and the SubTypeName coming from SubType.

public class TypeInfo 
{
   public int TypeId {get;set;}
   public string TypeName {get;set;}
   public int SubTypeId {get;set;}
   public string SubTypeName {get;set;}
}

Is there an easy way with linq?

Enigmativity · Accepted Answer · 2016-08-25 01:24:41Z

2

It's very straight forward:

List<Type> types = ...
List<SubType> subTypes = ...
List<Association> associations = ...

IEnumerable<TypeInfo> query =
    from type in types
    join association in associations on type.TypeId equals association.TypeId
    join subType in subTypes on association.SubTypeId equals subType.SubTypeId
    select new TypeInfo()
    {
        TypeId = association.TypeId,
        SubTypeId = association.SubTypeId,
        TypeName = type.TypeName,
        SubTypeName = subType.SubTypeName,
    };

List<TypeInfo> typeInfos = query.ToList();

answered Aug 25, 2016 at 1:24

Enigmativity

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1 Comment

Bryan Over a year ago

Thanks, that did it!

bvoleti · Accepted Answer · 2016-08-25 02:45:33Z

-1

Assuming types and subTypes are of type List and List respectively.

var associations = new List<Association>();
var typeInfoes = associations
                .Join(types, a => a.TypeId, t => t.TypeId,
                        (a, t) => new TypeInfo
                        {
                            TypeId = a.TypeId,
                            TypeName = t.TypeName,
                            SubTypeId = a.SubTypeId,
                            SubTypeName = ""
                        }
                )
                .Join(subTypes, ti => ti.SubTypeId, st => st.SubTypeId, 
                        (ti, st) => new TypeInfo
                        {
                            TypeId = ti.TypeId,
                            TypeName = ti.TypeName,
                            SubTypeId = ti.SubTypeId,
                            SubTypeName = st.SubTypeName
                        }
                )
                .ToList();

edited Aug 25, 2016 at 2:45

answered Aug 24, 2016 at 21:56

bvoleti

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1 Comment

bvoleti Over a year ago

Enigmativity answer is better as it uses join. Edited to use expression chain syntax as an alternative to query syntax for the join.

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