Up LINQ query examples

Ordering & Grouping operators

Last modified on August 15, 2012 17:21

Examples of the LINQ OrderBy, OrderByDescending, ThenBy, ThenByDescending and GroupBy are shown below.  In the examples below _em1 is an EntityManager.

C#
[Description("Select all customers ordered by ContactName.")]
public void LinqToEntities53() {
  var query = from c in _em1.Customers
              orderby c.ContactName
              select c;
  Assert.IsTrue(query.First().ContactName == "Alejandra Camino");
}

[Description("Select all customers ordered by ContactName descending.")]
public void LinqToEntities54() {
  var query = from c in _em1.Customers
              orderby c.CompanyName descending
              select c;
  Assert.IsTrue(query.First().CompanyName == "Wolski Zajazd");
}

[Description("Select an anonoymous type with all product IDs ordered by UnitsInStock.")]
public void LinqToEntities55() {
  var query = from p in _em1.Products
              orderby p.UnitsInStock
              select new { p.ProductID, p.UnitsInStock };
  Assert.IsTrue(query.First().ProductID == 5);
}

[Description("Select an anonoymous type with all product IDs ordered by UnitsInStock as a method query.")]
public void LinqToEntities56() {
  var query = _em1.Products.OrderBy(p => p.UnitsInStock)
      .Select(p2 => new { p2.ProductID, p2.UnitsInStock });
  Assert.IsTrue(query.First().ProductID == 5);
  Assert.IsTrue(query.First().UnitsInStock == 0);
}

[Description("Select all customers ordered by the descending region.")]
public void LinqToEntities57() {
  var query = from c in _em1.Customers
              orderby c.Address.Region descending
              select c;
  Assert.IsTrue(query.First().CustomerID == "SPLIR");
  Assert.IsTrue(query.First().Address.Region == "WY");
}

[Description("Select all customers ordered by the descending region as a method query.")]
public void LinqToEntities58() {
  var query = _em1.Customers.Select(c => c).OrderByDescending(c2 => c2.Address.Region);
  Assert.IsTrue(query.First().CustomerID == "SPLIR");
}

[Description("Select all customers ordered by the region, then the contact name.")]
public void LinqToEntities59() {
  var query = _em1.Customers.Select(c => c)
      .OrderBy(c => c.Address.Region).ThenBy(c => c.ContactName);
  Assert.IsTrue(query.First().CustomerID == "ROMEY");
  Assert.IsTrue(query.First().Address.City + "/" + query.First().ContactName == "Madrid/Alejandra Camino");
}

[Description("Select all customers ordered by the region in descending order, then the contact name.")]
public void LinqToEntities60() {
  var query = _em1.Customers.Select(c => c)
      .OrderByDescending(c => c.Address.Region).ThenBy(c => c.ContactName);
  Assert.IsTrue(query.First().CustomerID == "SPLIR");
}

[Description("Select all customers ordered by the region then the contact name in descending order.")]
public void LinqToEntities61() {
  var query = _em1.Customers.Select(c => c).OrderBy(c => c.Address.Region).ThenByDescending(c => c.ContactName);
  Assert.IsTrue(query.First().CustomerID == "WOLZA");

 ////Alternate
 //var query = _Em1.Customers.OrderBy(c => c.Address.Region).ThenByDescending(c => c.ContactName).Select(c => c);
}

[Description("Select all products ordered by the descending unit price.")]
public void LinqToEntities62() {
  var query = from p in _em1.Products
              orderby p.UnitPrice descending
              select p;
  Assert.IsTrue(query.First().ProductID == 38);

 //// Alternate
 //var query0 = _Em1.Products.OrderByDescending(p => p.UnitPrice).Select(p => p);
 //Assert.IsTrue(query0.First().ProductID == 38);}
}

[Description("Select all orders for a customer ordered by date that the order was placed.")]
public void LinqToEntities63() {

 // Alternate:
 //var query0 = _Em1.Customers.Where(c=>c.CustomerID == "ALFKI")
 //    .SelectMany(c => c.Orders).OrderBy(o => o.OrderDate);
 //Assert.IsTrue(query0.First().OrderDate  == new DateTime(1997,8,25));

  var query = _em1.Customers.Where(cust => cust.CustomerID == "ALFKI")
      .SelectMany(c => c.Orders.Select(o => o))
      .OrderBy(o2 => o2.OrderDate);

  Assert.IsTrue(query.First().OrderDate == new DateTime(1997, 8, 25));
}

[Description("Select all Regions with a customer.")]
public void LinqToEntities64() {
  var query = from c in _em1.Customers
              group c by c.Address.Region into regions
              select new { regions.Key };
  Assert.IsTrue(query.Count() == 19);

  var query2 = query.OrderByDescending(r => r.Key);
  Assert.IsTrue(query2.First().Key == "WY");
}

[Description("Select all dates with orders placed.")]
public void LinqToEntities65() {
  var query = from o in _em1.Orders
              group o by o.OrderDate into dates
              select new { dates.Key };
  Assert.IsTrue(query.Count() == 480);

  var query2 = query.OrderBy(d => d.Key);
  Assert.IsTrue(query2.First().Key == new DateTime(1996, 7, 4));
}

[Description("Select all Regions and customer count for each region.")]
public void LinqToEntities66() {
  var query = from c in _em1.Customers
              group c by c.Address.Region into regions
              orderby regions.Key
              select new { region = regions.Key, count = regions.Count() };
  var r = query.ToList();

  Assert.IsTrue(r.First().count == 60); // the variable count
}

[Description("Select all Regions and customer count for each region as a method query.")]
public void LinqToEntities67() {
  var query = _em1.Customers.GroupBy(c => c.Address.Region)
      .OrderByDescending(r => r.Key)
      .Select(r => new { region = r.Key, count = r.Count() });
  Assert.IsTrue(query.First().count == 1);
}

[Description("Select all Customer Regions with the total Freight on all orders for Customers in that Region.")]
public void LinqToEntities68() {
  var query = from c in _em1.Customers
              group c by c.Address.Region into regions
              orderby regions.Key
              join c2 in _em1.Customers on regions.Key equals c2.Address.Region
              select new { region = regions.Key, total = c2.Orders.Sum(o => o.Freight) };
  var r = query.ToList();
  Assert.IsTrue(query.First().region == null);
  Assert.IsTrue(query.First().total == 225.58M);
}

[Description("Select all Customer Regions with the total Freight on all orders for Customers in that Region as a method query.")]
public void LinqToEntities69() {
  var query = _em1.Customers.GroupBy(c => c.Address.Region)
      .OrderBy(r => r.Key)
      .Select(g => new {
        Region = g.Key,
        FreightTotal = g
            .SelectMany(c2 => c2.Orders)
            .Sum(o => o.Freight)
      });

  Assert.IsTrue(query.First().Region == null);
  Assert.IsTrue(query.First().FreightTotal == 38063.31M);

  var query2 = query.OrderByDescending(r => r.Region);
  Assert.IsTrue(query2.First().Region == "WY");
  Assert.IsTrue(query2.First().FreightTotal == 558.67M);
}
VB
<Description("Select all customers ordered by ContactName.")>
Public Sub LinqToEntities53()
 Dim query = From c In _em1.Customers
              Order By c.ContactName
             Select c
  Assert.IsTrue(query.First().ContactName = "Alejandra Camino")
End Sub

<Description("Select all customers ordered by ContactName descending.")>
Public Sub LinqToEntities54()
 Dim query = From c In _em1.Customers
              Order By c.CompanyName Descending
             Select c
  Assert.IsTrue(query.First().CompanyName = "Wolski Zajazd")
End Sub

<Description("Select an anonoymous type with all product IDs ordered by UnitsInStock.")>
Public Sub LinqToEntities55()
 Dim query = From p In _em1.Products
              Order By p.UnitsInStock
             Select New With {Key p.ProductID, Key p.UnitsInStock}
  Assert.IsTrue(query.First().ProductID = 5)
End Sub

<Description("Select an anonoymous type with all product IDs ordered by UnitsInStock as a method query.")>
Public Sub LinqToEntities56()
 Dim query = _em1.Products.OrderBy(Function(p) p.UnitsInStock).Select(Function(p2) New With {Key p2.ProductID, Key p2.UnitsInStock})
  Assert.IsTrue(query.First().ProductID = 5)
  Assert.IsTrue(query.First().UnitsInStock = 0)
End Sub

<Description("Select all customers ordered by the descending region.")>
Public Sub LinqToEntities57()
 Dim query = From c In _em1.Customers
              Order By c.Address.Region Descending
             Select c
  Assert.IsTrue(query.First().CustomerID = "SPLIR")
  Assert.IsTrue(query.First().Address.Region = "WY")
End Sub

<Description("Select all customers ordered by the descending region as a method query.")>
Public Sub LinqToEntities58()
 Dim query = _em1.Customers.Select(Function(c) c).OrderByDescending(Function(c2) c2.Address.Region)
  Assert.IsTrue(query.First().CustomerID = "SPLIR")
End Sub

<Description("Select all customers ordered by the region, then the contact name.")>
Public Sub LinqToEntities59()
 Dim query = _em1.Customers.Select(Function(c) c).OrderBy(Function(c) c.Address.Region).ThenBy(Function(c) c.ContactName)
  Assert.IsTrue(query.First().CustomerID = "ROMEY")
  Assert.IsTrue(query.First().Address.City & "/" & query.First().ContactName = "Madrid/Alejandra Camino")
End Sub

<Description("Select all customers ordered by the region in descending order, then the contact name.")>
Public Sub LinqToEntities60()
 Dim query = _em1.Customers.Select(Function(c) c).OrderByDescending(Function(c) c.Address.Region).ThenBy(Function(c) c.ContactName)
  Assert.IsTrue(query.First().CustomerID = "SPLIR")
End Sub

<Description("Select all customers ordered by the region then the contact name in descending order.")>
Public Sub LinqToEntities61()
 Dim query = _em1.Customers.Select(Function(c) c).OrderBy(Function(c) c.Address.Region).ThenByDescending(Function(c) c.ContactName)
  Assert.IsTrue(query.First().CustomerID = "WOLZA")

 '//Alternate
 'var query = _Em1.Customers.OrderBy(c => c.Address.Region).ThenByDescending(c => c.ContactName).Select(c => c);
End Sub

<Description("Select all products ordered by the descending unit price.")>
Public Sub LinqToEntities62()
 Dim query = From p In _em1.Products
              Order By p.UnitPrice Descending
             Select p
  Assert.IsTrue(query.First().ProductID = 38)

 '// Alternate
 'var query0 = _Em1.Products.OrderByDescending(p => p.UnitPrice).Select(p => p);
 'Assert.IsTrue(query0.First().ProductID == 38);}
End Sub

<Description("Select all orders for a customer ordered by date that the order was placed.")>
Public Sub LinqToEntities63()

 ' Alternate:
 'var query0 = _Em1.Customers.Where(c=>c.CustomerID == "ALFKI")
 '    .SelectMany(c => c.Orders).OrderBy(o => o.OrderDate);
 'Assert.IsTrue(query0.First().OrderDate  == new DateTime(1997,8,25));

 Dim query = _em1.Customers.Where(Function(cust) cust.CustomerID = "ALFKI").SelectMany(Function(c) c.Orders.Select(Function(o) o)).OrderBy(Function(o2) o2.OrderDate)

  Assert.IsTrue(query.First().OrderDate = New Date(1997, 8, 25))
End Sub

<Description("Select all Regions with a customer.")>
Public Sub LinqToEntities64()
 Dim query = From c In _em1.Customers
              Group c By c.Address.Region Into regions = Group
             Select New With {Key Region}
  Assert.IsTrue(query.Count() = 19)

 Dim query2 = query.OrderByDescending(Function(r) r.Key)
  Assert.IsTrue(query2.First().Key = "WY")
End Sub

<Description("Select all dates with orders placed.")>
Public Sub LinqToEntities65()
 Dim query = From o In _em1.Orders
              Group o By o.OrderDate Into dates = Group
             Select New With {Key OrderDate}
  Assert.IsTrue(query.Count() = 480)

 Dim query2 = query.OrderBy(Function(d) d.Key)
  Assert.IsTrue(query2.First().Key = New Date(1996, 7, 4))
End Sub

<Description("Select all Regions and customer count for each region.")>
Public Sub LinqToEntities66()
 Dim query = From c In _em1.Customers
              Group c By c.Address.Region Into regions = Group
              Order By Region
             Select New With {Key .region = Region, Key .count = regions.Count()}
 Dim r = query.ToList()

  Assert.IsTrue(r.First().count = 60) ' the variable count
End Sub

<Description("Select all Regions and customer count for each region as a method query.")>
Public Sub LinqToEntities67()
 Dim query = _em1.Customers.GroupBy(Function(c) c.Address.Region).OrderByDescending(Function(r) r.Key).Select(Function(r) New With {Key .region = r.Key, Key .count = r.Count()})
  Assert.IsTrue(query.First().count = 1)
End Sub

<Description("Select all Customer Regions with the total Freight on all orders for Customers in that Region.")>
Public Sub LinqToEntities68()
 Dim query = From c In _em1.Customers
              Group c By c.Address.Region Into regions = Group
              Order By Region
              Join c2 In _em1.Customers On Region Equals c2.Address.Region
             Select New With {Key .region = Region, Key .total = c2.Orders.Sum(Function(o) o.Freight)}
 Dim r = query.ToList()
  Assert.IsTrue(query.First().region Is Nothing)
  Assert.IsTrue(query.First().total = 225.58D)
End Sub

<Description("Select all Customer Regions with the total Freight on all orders for Customers in that Region as a method query.")>
Public Sub LinqToEntities69()
 Dim query = _em1.Customers.GroupBy(Function(c) c.Address.Region).OrderBy(Function(r) r.Key).Select(Function(g) New With {Key .Region = g.Key, Key .FreightTotal = g.SelectMany(Function(c2) c2.Orders).Sum(Function(o) o.Freight)})

  Assert.IsTrue(query.First().Region Is Nothing)
  Assert.IsTrue(query.First().FreightTotal = 38063.31D)

 Dim query2 = query.OrderByDescending(Function(r) r.Region)
  Assert.IsTrue(query2.First().Region = "WY")
  Assert.IsTrue(query2.First().FreightTotal = 558.67D)
End Sub
Tags: Query
Created by DevForce on February 18, 2011 04:27

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