如何使用LINQ从DataView中选择多个字段并应用.Distinct（）

Question

I want to select some fields from DataView and after selecting those fields want to apply .Distinct() on these set of fields.

Right now, I used this code :

DataView dvGroups = new DataView();
dvGroups = GetDataFromDatabase(); //-- Fill Dataview
var groups = dvGroups.Table.AsEnumerable()
                           .Where(x => x.Field<int>("GroupId") != 0)
                           .Select(p => p.Field<int>("GroupId"))
                           .Distinct()
                           .ToArray();

it's only selecting a single field (ie "GroupId" ). But, Now i want to select multiple fields (like "GroupId", "GroupName" ) and then get the distinct value.

How can i achieve this task?

Answer 1

You can create anonymous objects:

.Select(p => new {
    GroupId = p.Field<int>("GroupId"),
    Something = p.Field<string>("Something"),
})
.Distinct().ToArray();

for example, because anonymous types are "compatible" with Distinct() (see LINQ Select Distinct with Anonymous Types ), because the compiler generates the Equals / GetHashCode methods.

Or you could use the Tuple :

.Select(p => Tuple.Create(p.Field<int>("GroupId"), p.Field<string>("Something")))

But they are normally less clear.

More complex is to create your class and implement the Equals and GetHashCode

Answer 2

You can use an anonymous type:

var groups = dvGroups.Table
          .AsEnumerable()
          .Where(x => x.Field<int>("GroupId") != 0)
           .Select(p => new 
                        { 
                            id = p.Field<int> ("GroupId"),
                            name = p.Field<string> ("Name"))
                        }).Distinct().ToArray();