I am working with Entity Framework. I am retrieving data using a query with .Where
and .Select
conditions.
var myData = await _dbContext.Samples.Include(i => i.Experiment)
.Include(i => i.Experiment.Test)
.Include(i => i.Experiment.Test.Project)
.Include(i => i.Samples)
.Where(i => i.Experiment.Test.Status == 3 && i.Experiment.Test.TestId == 3)
.Select( e => new ExperimentCollections() {
ExperimentNumber = e.Experiment.Test.ExperimentNumber,
ExperimentName = e.Experiment.Test.Project.Name
}).ToListAsync();
There can be multiple rows with the same ExperimentNumber
and I need to avoid it from inserting into myData
.
For example: in myData
:
myData[0]
ExperimentNumber: 1520,
ExperimentName: ABC
myData[1]
ExperimentNumber: 1521,
ExperimentName: EFG
myData[2]
ExperimentNumber: 1520,
ExperimentName: HIJ
I need to avoid myData[2]
data to be inserted into myData
using Entity Framework in single single query without using foreach loop.
I tried following code with.Distinct()
var myData = await _dbContext.Samples.Include(i => i.Experiment)
.Include(i => i.Experiment.Test)
.Include(i => i.Experiment.Test.Project)
.Include(i => i.Samples)
.Where(i => i.Experiment.Test.Status == 3 && i.Experiment.Test.TestId == 3)
.Select( e => new ExperimentCollections() {
ExperimentNumber = e.Experiment.Test.ExperimentNumber,
ExperimentName = e.Experiment.Test.Project.Name
}).Distinct().ToListAsync();
And I even tried.Distinct().OrderBy(i => i.TestNumber) too.
The GROUP BY
statement is often used with aggregate functions ( COUNT, MAX, MIN, SUM, AVG
) to group the result-set by one or more columns.
After Where clause use GROUP BY column_name(s)
.
You can try to use Extend method to avoid same data in the list.
public static class Extend
{
public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector)
{
HashSet<TKey> seenKeys = new HashSet<TKey>();
foreach (TSource element in source)
{
if (seenKeys.Add(keySelector(element)))
{
yield return element;
}
}
}
}
You can use it like the following code:
var query = data.DistinctBy(p => p.ExperimentNumber).ToList();
foreach (var item in query)
{
Console.WriteLine(item.ExperimentName+" "+item.ExperimentNumber);
}
Result:
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.