c# - Why is Dictionary.ToLookup() not working? -

i have dictionary<ttype, list<tdata>> represents kind of internal data container. tdata elements grouped ttype.

a user may query dictionary , should given ilookup<ttype, tdata> result. simplest query return whole data container:

public ilookup<ttype, tdata> queryeverything () {     return _data.tolookup(kvp => kvp.key, kvp => kvp.value); } 

however, not work. why? isn't lookup nothing more dictionary of key => ienumerable<value>?

you try this:

public ilookup<ttype, tdata> queryeverything () {     return _data.selectmany(kvp => p.value.select(x => new { kvp.key, value = x }))                 .tolookup(kvp => kvp.key, kvp => kvp.value); } 

of course, instead of anonymous type, create keyvaluepair<ttype, tdata> or tuple<ttype, tdata> easily.

or perhaps better solution (if can manage refactor code) change private _data dictionary ilookup<ttype, tdata>, there no need convert dictionary in first place.