ObjectQuery<T>.GroupBy(String, String, ObjectParameter[]) Method
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Groups the query results by the specified criteria.
public:
System::Data::Objects::ObjectQuery<System::Data::Common::DbDataRecord ^> ^ GroupBy(System::String ^ keys, System::String ^ projection, ... cli::array <System::Data::Objects::ObjectParameter ^> ^ parameters);
public System.Data.Objects.ObjectQuery<System.Data.Common.DbDataRecord> GroupBy (string keys, string projection, params System.Data.Objects.ObjectParameter[] parameters);
member this.GroupBy : string * string * System.Data.Objects.ObjectParameter[] -> System.Data.Objects.ObjectQuery<System.Data.Common.DbDataRecord>
Public Function GroupBy (keys As String, projection As String, ParamArray parameters As ObjectParameter()) As ObjectQuery(Of DbDataRecord)
- keys
- String
The key columns by which to group the results.
- projection
- String
The list of selected properties that defines the projection.
- parameters
- ObjectParameter[]
Zero or more parameters that are used in this method.
A new ObjectQuery<T> instance of type DbDataRecord that is equivalent to the original instance with GROUP BY applied.
The query
parameter is null
or an empty string.
-or-
The projection
parameter is null
or an empty string.
This example creates a new ObjectQuery<T> object that contains the results of the existing query grouped by product name.
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
string queryString = @"SELECT VALUE product
FROM AdventureWorksEntities.Products AS product";
ObjectQuery<Product> productQuery =
new ObjectQuery<Product>(queryString,
context, MergeOption.NoTracking);
ObjectQuery<DbDataRecord> productQuery2 =
productQuery.GroupBy("it.name AS pn",
"Sqlserver.COUNT(it.Name) as count, pn");
// Iterate through the collection of Products
// after the GroupBy method was called.
foreach (DbDataRecord result in productQuery2)
{
Console.WriteLine("Name: {0}; Count: {1}",
result["pn"], result["count"]);
}
}
}
This example returns a set of nested data records that contain the Contact.LastName
column, grouped and sorted alphabetically by the first letter of Contact.LastName
.
using (AdventureWorksEntities context =
new AdventureWorksEntities())
{
// Define the query with a GROUP BY clause that returns
// a set of nested LastName records grouped by first letter.
ObjectQuery<DbDataRecord> query =
context.Contacts
.GroupBy("SUBSTRING(it.LastName, 1, 1) AS ln", "ln")
.Select("it.ln AS ln, (SELECT c1.LastName " +
"FROM AdventureWorksEntities.Contacts AS c1 " +
"WHERE SubString(c1.LastName, 1, 1) = it.ln) AS CONTACT")
.OrderBy("it.ln");
// Execute the query and walk through the nested records.
foreach (DbDataRecord rec in
query.Execute(MergeOption.AppendOnly))
{
Console.WriteLine("Last names that start with the letter '{0}':",
rec[0]);
List<DbDataRecord> list = rec[1] as List<DbDataRecord>;
foreach (DbDataRecord r in list)
{
for (int i = 0; i < r.FieldCount; i++)
{
Console.WriteLine(" {0} ", r[i]);
}
}
}
}
GroupBy applies the projection specified by the projection
parameter. This means that the ObjectQuery<T> returned by the GroupBy method is always of type DbDataRecord. For more information, see Object Queries.
Produkt | Versjoner |
---|---|
.NET Framework | 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
.NET-tilbakemelding
.NET er et åpen kilde-prosjekt. Velg en kobling for å gi tilbakemelding: