Convert 2 foreach loops which has lambda expressions to one or two lambda statements in order to remove for each loops

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Hi,

I need to convert 2 for each loops which are shown as below to linq -

List<Company> res = new List<Company>();
          List<EmployeeCount> result = new List<EmployeeCount>();
          foreach (string s in indType)
          {
              List<Company> re = _entities.Company.Where(a => Convert.ToString(a.industry_id.ToLower()).Equals(s.ToLower().ToString())).ToList();
              res.AddRange(re);
          }

          foreach (Company r in res)
          {
              List<EmployeeCount> empCount = await _entities.EmployeeCount.Where(a => Convert.ToString(a.Company_ID.ToLower()).Equals(r.Company_id.ToLower())).Select((a => new EmployeeCount() { Company_ID = a.Company_ID, Industry_ID = a.Industry_ID, Company_Name = a.Company_Name, City = a.City, Number_Employees = a.Number_Employees })).ToListAsync();
              result.AddRange(empCount);
          }
          return result.AsQueryable();

I need to optimize these foreach loops using lambda expressions in order to fetch the data fastly. Please help me on this.

What I have tried:

tried like below -

res.ForEach(i => i.company_id).intersect(_entities.EmployeeCount.Select(i => i.company_id).ToList();

its showing it returns List<string> only, I need List<employeecount>. Unable to select the values of EmployeeCount entity.

Posted 20-Jul-18 1:51am

sri4dotnet

Updated 20-Jul-18 4:54am

v2

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F-ES Sitecore 20-Jul-18 7:56am

Your linq loops will probably be slower than your existing code. Linq is not for performance. If that's your aim then leave your code as it is.

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Richard Deeming · Answer 1 · 2018-07-20T04:48:00

Not entirely clear what you're trying to do, but assuming you're using Entity Framework, something like this should work:

C#

return _entities.EmployeeCount.Where(ec => indType.Contains(ec.Industry_ID));

If the Industry_ID column on the EmployeeCount entity doesn't match the column of the same name on the Company entity, then you'll need a navigation property:

C#

return _entities.EmployeeCount.Where(ec => indType.Contains(ec.Company.Industry_ID));

If the EmployeeCount set doesn't return an instance of your EmployeeCount class, then add a .Select(...) to the end:

C#

return _entities.EmployeeCount
    .Where(ec => indType.Contains(ec.Industry_ID))
    .Select(ec => new EmployeeCount
    {
        Company_ID = ec.Company_ID, 
        Industry_ID = ec.Industry_ID, 
        Company_Name = ec.Company_Name, 
        City = ec.City, 
        Number_Employees = ec.Number_Employees,
    });

TheFoZ · Answer 2 · 2018-07-20T04:54:00

If you are looking for speed, loops are the way to go.

I would take a look at your data. Does every company have an employee count? If they do then there is not a need for the first loop. All the first loop does is get a list of Company IDs based on Industry ID that you are then using in the second loop which also has Industry ID.

Do you also need to make a new instance of EmployeeCount or can you use the original object? Using the original will save time rather than creating a new instance.

I would do something similar to this if the first loop doesn't matter and you do not need a copy of the object

List<EmployeeCount> result = new List<EmployeeCount>();

foreach (EmployeeCount c in _entities.EmployeeCount)
{
    if (indType.Contains(c.industry_id))
    {
        result.Add(c);
    }
}

return result;

Convert 2 foreach loops which has lambda expressions to one or two lambda statements in order to remove for each loops

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