ObjectQuery<T>.GroupBy(String, String, ObjectParameter[]) Method
Definition
Important
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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)
Parameters
- 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.
Returns
A new ObjectQuery<T> instance of type DbDataRecord that is equivalent to the original instance with GROUP BY applied.
Exceptions
The query
parameter is null
or an empty string.
-or-
The projection
parameter is null
or an empty string.
Examples
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]);
}
}
}
}
Remarks
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.