Fix open issues

- Fixes #43760: Update where clause to filter out some values. Update output comment.
- Fixes #43765:  Update `let` statement so the query result isn't empty.
- Fixes #43766: Update query parameters so the result set isn't empty.
- Fixes #43768: Add sample data
- Fixes #43790: Audit all samples in this article and ensure all have output.
- Fixes #43809:  Update samples to include the data sources.

While doing this, update the project to .NET 9

Author: BillWagner

docs/csharp/linq/get-started/query-expression-basics.md

@@ -1,7 +1,7 @@
 ---
 title: Query expression basics (LINQ)
 description: Introduces concepts related to query expressions
-ms.date: 03/06/2024
+ms.date: 01/16/2025
 ---
 # Query expression basics
 

docs/csharp/linq/get-started/snippets/SnippetApp/Basics.cs

@@ -3,7 +3,9 @@
 public static class Basics
 {
 
-    static readonly int[] scores = [0]; // Max is called on this, so one value is needed
+    static readonly int[] scores = [
+        0, 30, 50, 70, 80, 85, 94, 87, 96, 88, 59, 90, 91, 85, 60, 49, 100
+        ];
 
     // <SourceData>
     static readonly City[] cities = [
@@ -50,6 +52,10 @@ where score > 80
             orderby score descending
             select score;
         // </basics1>
+        foreach(var score in highScoresQuery)
+        {
+            Console.WriteLine(score);
+        }
     }
 
     public static void Basics2()
@@ -61,6 +67,10 @@ where score > 80
             orderby score descending
             select $"The score is {score}";
         // </basics2>
+        foreach (var score in highScoresQuery2)
+        {
+            Console.WriteLine(score);
+        }
     }
 
     public static void Basics3()
@@ -72,6 +82,7 @@ where score > 80
             select score
         ).Count();
         // </basics3>
+        Console.WriteLine($"highest score: {highScoreCount}");
     }
 
     public static void Basics4()
@@ -84,6 +95,7 @@ where score > 80
 
         var scoreCount = highScoresQuery3.Count();
         // </basics4>
+        Console.WriteLine($"highest score: {scoreCount}");
     }
 
     public static void Basics5()
@@ -122,7 +134,7 @@ public static void Basics6()
         //Query syntax
         IEnumerable<City> queryMajorCities =
             from city in cities
-            where city.Population > 100000
+            where city.Population > 30_000_000
             select city;
 
         // Execute the query to produce the results
@@ -132,12 +144,19 @@ where city.Population > 100000
         }
 
         // Output:
-        // City { Population = 120000 }
-        // City { Population = 112000 }
-        // City { Population = 150340 }
-
+        // City { Name = Tokyo, Population = 37833000 }
+        // City { Name = Delhi, Population = 30290000 }
+        
         // Method-based syntax
-        IEnumerable<City> queryMajorCities2 = cities.Where(c => c.Population > 100000);
+        IEnumerable<City> queryMajorCities2 = cities.Where(c => c.Population > 30_000_000);
+        // Execute the query to produce the results
+        foreach (City city in queryMajorCities2)
+        {
+            Console.WriteLine(city);
+        }
+        // Output:
+        // City { Name = Tokyo, Population = 37833000 }
+        // City { Name = Delhi, Population = 30290000 }
         // </basics6>
     }
 
@@ -158,6 +177,8 @@ from score in scores
         // the following returns the same result
         highScore = scores.Max();
         // </basics7>
+        Console.WriteLine($"highest score: {highestScore}");
+        Console.WriteLine($"high Score: {highScore}");
     }
 
     public static void Basics7a()
@@ -178,6 +199,14 @@ where city.Population > 10000
             select city;
         var largeCitiesList2 = largeCitiesQuery.ToList();
         // </basics7a>
+        foreach(var item in largeCitiesList)
+        {
+            Console.WriteLine(item.Name + ":" + item.Population);
+        }
+        foreach (var item in largeCitiesList2)
+        {
+            Console.WriteLine(item.Name + ":" + item.Population);
+        }
     }
 
     public static void Basics8()
@@ -188,16 +217,24 @@ from city in cities
             where city.Population > 100000
             select city;
         // </basics8>
+        foreach (var city in queryCities)
+        {
+            Console.WriteLine(city.Name + ":" + city.Population);
+        }
     }
 
     public static void Basics9()
     {
         // <basics9>
         IEnumerable<Country> countryAreaQuery =
             from country in countries
-            where country.Area > 500000 //sq km
+            where country.Area > 20 //sq km
             select country;
         // </basics9>
+        foreach (var country in countryAreaQuery)
+        {
+            Console.WriteLine(country.Name + ":" + country.Area);
+        }
     }
 
     public static void Basics10()
@@ -209,6 +246,10 @@ from city in country.Cities
             where city.Population > 10000
             select city;
         // </basics10>
+        foreach (var city in cityQuery)
+        {
+            Console.WriteLine(city.Name + ":" + city.Population);
+        }
     }
 
     public static void Basics11()
@@ -218,6 +259,14 @@ public static void Basics11()
             from country in countries
             group country by country.Name[0];
         // </basics11>
+        foreach (var group in queryCountryGroups)
+        {
+            Console.WriteLine(group.Key);
+            foreach (var country in group)
+            {
+                Console.WriteLine(country.Name);
+            }
+        }
     }
 
     public static void Basics12()
@@ -228,6 +277,10 @@ from country in countries
             orderby country.Area
             select country;
         // </basics12>
+        foreach (var country in sortedQuery)
+        {
+            Console.WriteLine(country.Name + ":" + country.Area);
+        }
     }
 
     public static void Basics13()
@@ -241,6 +294,10 @@ from country in countries
                 Pop = country.Population
             };
         // </basics13>
+        foreach (var item in queryNameAndPop)
+        {
+            Console.WriteLine(item.Name + ":" + item.Pop);
+        }
     }
 
     public static void Basics14()
@@ -249,7 +306,7 @@ public static void Basics14()
         // percentileQuery is an IEnumerable<IGrouping<int, Country>>
         var percentileQuery =
             from country in countries
-            let percentile = (int)country.Population / 10_000_000
+            let percentile = (int)country.Population / 1_000
             group country by percentile into countryGroup
             where countryGroup.Key >= 20
             orderby countryGroup.Key
@@ -272,9 +329,13 @@ public static void Basics15()
         // <basics15>
         IEnumerable<City> queryCityPop =
             from city in cities
-            where city.Population is < 200000 and > 100000
+            where city.Population is < 15_000_000 and > 10_000_000
             select city;
         // </basics15>
+        foreach (var city in queryCityPop)
+        {
+            Console.WriteLine(city.Name + ":" + city.Population);
+        }   
     }
 
     public static void Basics16()
@@ -285,12 +346,24 @@ from country in countries
             orderby country.Area, country.Population descending
             select country;
         // </basics16>
+        foreach (var country in querySortedCountries)
+        {
+            Console.WriteLine(country.Name + ":" + country.Area + ":" + country.Population);
+        }
     }
 
     public static void Basics17()
     {
-        string[] categories = [];
-        Product[] products = [];
+        string[] categories = ["brass", "winds", "percussion"];
+        Product[] products = [
+            new Product("Trumpet", "brass"),
+            new Product("Trombone", "brass"),
+            new Product("French Horn", "brass"),
+            new Product("Clarinet", "winds"),
+            new Product("Flute", "winds"),
+            new Product("Cymbal", "percussion"),
+            new Product("Drum", "percussion")
+            ];
 
         // <basics17>
         var categoryQuery =
@@ -302,6 +375,10 @@ join prod in products on cat equals prod.Category
                 Name = prod.Name
             };
         // </basics17>
+        foreach (var item in categoryQuery)
+        {
+            Console.WriteLine(item.Category + ":" + item.Name);
+        }
     }
 
     public static void Basics18()
@@ -339,5 +416,9 @@ select student2.ExamScores.Average()
                 ).Max()
             };
         // </basics19>
+        foreach (var item in queryGroupMax)
+        {
+            Console.WriteLine(item.Level + ":" + item.HighestScore);
+        }
     }
 }

docs/csharp/linq/get-started/snippets/SnippetApp/LinqGetStarted.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFramework>net9.0</TargetFramework>
     <RootNamespace>Linq.GetStarted</RootNamespace>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>

docs/csharp/linq/get-started/snippets/SnippetApp/NullValues.cs

@@ -1,12 +1,37 @@
 namespace LinqSamples;
 
+// <dataSourceTypes>
 record Product(string Name, int CategoryID);
 record Category(string Name, int ID);
+// </dataSourceTypes>
+
 
 public static class NullValues
 {
-    static readonly Category[] categories = [];
-    static readonly Product[] products = [];
+    // <source>
+    static Category?[] categories =
+    [
+        new ("brass", 1),
+        null,
+        new ("winds", 2),
+        default,
+        new ("percussion", 3)
+    ];
+
+    static Product?[] products =
+    [
+        new Product("Trumpet", 1),
+        new Product("Trombone", 1),
+        new Product("French Horn", 1),
+        null,
+        new Product("Clarinet", 2),
+        new Product("Flute", 2),
+        null,
+        new Product("Cymbal", 3),
+        new Product("Drum", 3)
+    ];
+    // </source>
+
 
     public static void NullValues1()
     {

docs/csharp/linq/get-started/snippets/SnippetApp/Program.cs

@@ -2,6 +2,7 @@
 
 WriteSeparator(nameof(PartsOfAQuery));
 PartsOfAQuery();
+Console.WriteLine();
 
 WriteSeparator(nameof(Linq.GetStarted.Basics.Basics1));
 Linq.GetStarted.Basics.Basics1();
@@ -41,6 +42,7 @@
 Linq.GetStarted.Basics.Basics17();
 WriteSeparator(nameof(Linq.GetStarted.Basics.Basics18));
 Linq.GetStarted.Basics.Basics18();
+Console.WriteLine();
 WriteSeparator(nameof(Linq.GetStarted.Basics.Basics19));
 Linq.GetStarted.Basics.Basics19();
 

docs/csharp/linq/get-started/write-linq-queries.md

@@ -1,7 +1,7 @@
 ---
 title: Write LINQ queries
 description: Learn how to write LINQ queries in C#.
-ms.date: 04/19/2024
+ms.date: 01/16/2025
 ---
 # Write C# LINQ queries to query data
 
@@ -96,6 +96,13 @@ In some cases, you don't know until run time how many predicates you have to app
 
 :::code language="csharp" source="./snippets/SnippetApp/RuntimeFiltering.cs" id="runtime_filtering_1":::
 
+> [!NOTE]
+> This example uses the following data source and data:
+
+:::code language="csharp" source="./snippets/SnippetApp/DataSources.cs" id="basics_datasource":::
+
+:::code language="csharp" source="./snippets/SnippetApp/Basics.cs" id="SourceData":::
+
 You can use control flow statements, such as `if... else` or `switch`, to select among predetermined alternative queries. In the following example, `studentQuery` uses a different `where` clause if the run-time value of `oddYear` is `true` or `false`.
 
 :::code language="csharp" source="./snippets/SnippetApp/RuntimeFiltering.cs" id="runtime_filtering_2":::
@@ -104,6 +111,12 @@ You can use control flow statements, such as `if... else` or `switch`, to select
 
 This example shows how to handle possible null values in source collections. An object collection such as an <xref:System.Collections.Generic.IEnumerable%601> can contain elements whose value is [null](../../language-reference/keywords/null.md). If a source collection is `null` or contains an element whose value is `null`, and your query doesn't handle `null` values, a <xref:System.NullReferenceException> is thrown when you execute the query.
 
+The following example uses these types and static data arrays:
+
+:::code language="csharp" source="./snippets/SnippetApp/NullValues.cs" id="dataSourceTypes":::
+
+:::code language="csharp" source="./snippets/SnippetApp/NullValues.cs" id="source":::
+
 You can code defensively to avoid a null reference exception as shown in the following example:
 
 :::code language="csharp" source="./snippets/SnippetApp/NullValues.cs" id="null_values_1":::