linq from a list inside a class

Question

linq from a list inside a class

Anjali Agarwal 1,531

i have the following Model class:

public partial class EmployeeInfo

{

public int EmployeeInfoId { get; set; }

public string FirstName { get; set; } = null!;

public int? JobTitleLookupId { get; set; }

public virtual JobTitleLookup? JobTitleLookup { get; set; }

}

public partial class JobTitleLookup

{

public int JobTitleLookupId { get; set; }

public string Title { get; set; } = null!;

public virtual ICollection<EmployeeInfo> EmployeeInfos { get; } = new List<EmployeeInfo>();

}

I have JobTitleLookupId in my employeeeInfo database table. How can i get

the name of the jobtitle if i have the corresponding ID in employeeInfo Table.

belows is my JobTitleLookup table:

JobTitleLookupID   title
1                   title1
2                   title2
3                   title3

EmployeeInfo table

EmployeeInfoId FirstName JobTitleLookupID
1                test1     2
2                test3     1
3                 testx     3

how can I get Title using LINQ if I query the employeeInfo table.

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Answer 1

Anonymous

Hi @Anjali Agarwal

I have JobTitleLookupId in my employeeeInfo database table. How can i get the name of the jobtitle if i have the corresponding ID in employeeInfo Table. how can I get Title using LINQ if I query the employeeInfo table.

You can get the job title according to the Navigation property: JobTitleLookup.

The LINQ query statement as below: use Inculde method to load the related entity. More detail information, see Eager Loading of Related Data.

            var id = 2;
            var query = _dbcontext.EmployeeInfos
                        .Include(c => c.JobTitleLookup)
                        .Where(c => c.EmployeeInfoId == id)
                        .Select(c => new
                        {
                            EmployeeInformId = c.EmployeeInfoId,
                            FirstName = c.FirstName,
                            Title = c.JobTitleLookup==null?"null":c.JobTitleLookup.Title
                        }).ToList();

The result as below:

User's image

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Best regards,

Dillion

Anjali Agarwal 1,531

Hello @Anonymous , My Model class is very small in my question above, but in reality, its huge. I really dont want to write all the properties in the LINQ query. is their any faster way. below is what my query has become and I know, it will becom really big if I keep writing all the properties

   var query = await _ackContext.EmployeeInfos
                      .Include(c => c.JobTitleLookup)
                      .Where(c => c.EmployeeNumber == employeeId)
                      .Select(c => new
                      {

                          Title = c.JobTitleLookup == null ? "null" : c.JobTitleLookup.Title
                      }).LastAsync();

any help will be appreciated. Also what will be the return type of this query. I keep getting this error:

Cannot implicitly convert type 'System.Collections.Generic.List<<anonymous type: string Title>>' to 'System.Collections.Generic.List<object> when i write this:

    public async Task<List<string?>> GetJobTitle(string employeeId)
        {

            var query = await _ackContext.EmployeeInfos
                      .Include(c => c.JobTitleLookup)
                      .Where(c => c.EmployeeNumber == employeeId)
                      .Select(c => new 
                      {
                          
                          Title = c.JobTitleLookup == null ? "null" : c.JobTitleLookup.Title
                      }).ToListAsync();

            return query;
        }

Anonymous

Hi @Anjali Agarwal

I really dont want to write all the properties in the LINQ query. is their any faster way. below is what my query has become and I know, it will becom really big if I keep writing all the properties

You can select the EmployeeInfos in the LINQ statement, then the filtered EmployeeInfos contains the JobTitleLookup property, after that, when you want to display the title, just using the JobTitleLookup property. code like this:

            EmployeeInfo query2 = await _dbcontext.EmployeeInfos
                        .Include(c => c.JobTitleLookup)
                        .Where(c => c.EmployeeInfoId == id)
                        .OrderBy(c => c.EmployeeInfoId)
                        .LastAsync();

            var title = query2.JobTitleLookup==null ? "null" : query2.JobTitleLookup.Title;

The result as below: Note: when using LastAsync(), we have to sort the data.

User's image

Cannot implicitly convert type 'System.Collections.Generic.List<<anonymous type: string Title>>' to 'System.Collections.Generic.List<object> when i write this:

About this issue, since in the LINQ select clause, we use new to create object, so we get a list of objects. Here I suggest you can create model based on the selected property, such as below:

    public class EmployeeViewModel
    {
        public int EmployeeInformId { get; set; }
        public string FirstName { get; set; }
        public string Title { get; set; }
    }

Then, the query statement like this:

 public async Task<List<EmployeeViewModel>> GetJobTitle(string employeeId)
 {
            List<EmployeeViewModel> query = _dbcontext.EmployeeInfos
                        .Include(c => c.JobTitleLookup)
                        .Where(c => c.EmployeeInfoId == id)
                        .Select(c => new EmployeeViewModel()
                        {
                            EmployeeInformId = c.EmployeeInfoId,
                            FirstName = c.FirstName,
                            Title = c.JobTitleLookup==null?"null":c.JobTitleLookup.Title
                        }).ToList();
          return query;
}

Best regards,
Dillion

Anjali Agarwal 1,531 Reputation points

2023-02-10T18:27:02.7433333+00:00

Thank you!

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linq from a list inside a class

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