如何将来自同一IQueryable的不同行分组

Question

I have an IQueryable that contains the list of usage data in my application. Each row in it is a separate entry in the table. The structure is like this

{

Usagedata

Username (string)
SessionId (string)
PartOfAppAccessed
(
Key (int),
Name (string),
Description (string)
Time (DateTime)
)
}

But while displaying this data, I want to group rows based on session Id's. So my output has to be in this structure

{

Usagedata

Username (string)
SessionId (string)
Time (DateTime)
PartOfAppAccessed
(
Key (int),
Name (string),
Description (string)
Time (DateTime)
),
(
Key (int),
Name (string),
Description (string)
Time (DateTime)
),
(
Key (int),
Name (string),
Description (string)
Time (DateTime)
)
}

So my question is - How do I group different rows from the same IQueryable based on some condition (such as common sessionId's in this case)?

Answer 1

I suppose that you want to group your UsageData instances based on their SessionId and UserName . The code:

IQueryable<UsageData> usageData = ... ;
var groupedUsageData = usageData.GroupBy(x => new { x.SessionId, x.Username });

Then, you can work with a single group like the following:

var singleGroup = groupedUsageData.ElementAt(0);
string sessionId = singleGroup.Key.SessionId;
string name = singleGroup.Key.Name;

IEnumerable<string> accessedAppsNames = singleGroup.Select(x => x.PartOfAppAccessed.Name);

A few notes that came to mind:

• Since you can probably directly map the session to the user, it may be unnecessary to store both SessionId and Username in your UsageData objects. Perhaps it would be better to store only SessionId and get the name of the user from some other table?
• It doesn't make a sense for grouped UsageData to contain Time property. What value would it have? In your original object (before the grouping takes place), the Time property is only declared on PartOfAppAccessed object.