Linq - Loop through list of strings and add results to var variable

Question

I have my code sample below.

List<string> userIds = userAppService.GetUserIds()
    .Where(usr => usr.Status == "Active")
    .Select(u => u.User_Id)
    .ToList();

Now i would like loop through list of above UserId's and add the result to var variable.

foreach(string str in userIds)
{
    var result = SLSDBContext.USER_HISTORY
        .Where(i => i.UserId == str)
        .Select(x => new 
        {
            x.UserId,
            x.LogCount,
            x.IsRegistered 
        });

    return this.Json(result)
}

The problem with above is i will not be able to access 'result' variale outside of foreach block.. If i am trying yo declare 'result' variable before foreach block i am not able to assign the type to it.

any better way to get the desired result ?

I tried using Any() operator in Linq but i am not able to get the desired result.

var result = SLSDBContext.USER_HISTORY
    .Where(i => i.UserId.Contains(userIds))
    .Select(x => new 
    {
        x.UserId,
        x.LogCount,
        x.IsRegistered 
    });

do you want to append the result of the current interation on every iteration, or replace the previous (because that's what you're currently doing)? — MakePeaceGreatAgain
– MakePeaceGreatAgain, Commented Dec 28, 2022 at 11:15
I'm almost sure you need Where(i => userIds.Contains(i.UserId)), not Where(i => i.UserId.contains(userIds)) — MakePeaceGreatAgain
– MakePeaceGreatAgain, Commented Dec 28, 2022 at 11:17

Tim Schmelter · Accepted Answer · 2022-12-28 11:18:53Z

2

You could use a Join:

var activeUsers = userAppService.GetUserIds()
    .Where(usr => usr.Status == "Active");
var result = from uh in SLSDBContext.USER_HISTORY
             join au in activeUsers
                 on uh.UserId equals au.User_Id
             select new {
                 uh.UserId,
                 uh.LogCount,
                 uh.IsRegistered 
             };    

return this.Json(result.ToList());

answered Dec 28, 2022 at 11:18

Tim Schmelter

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Comments

Vivek Nuna · Accepted Answer · 2022-12-28 11:27:50Z

0

you can initialize the result before loop and use Concat method.

var result = Enumerable.Empty<USER_HISTORY>();

foreach(string str in userIds)
{
    result = result.Concat(SLSDBContext.USER_HISTORY.Where(i => i.UserId == str).Select(x => new {
      x.UserId,
      x.LogCount,
      x.IsRegistered 
    }));
}

return this.Json(result);

answered Dec 28, 2022 at 11:27

Vivek Nuna

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