Enhance documentation for TheoryData, MemberData, and ClassData in xUnit with additional examples and explanations

Author: vivekkpatel

docs/UnitTest/3 Class.md

@@ -4,7 +4,12 @@
 - So TheoryData is a built-in class in xUnit that helps you manage and provide complex data sets for parameterized tests.
 - It allows you to create **strongly-typed** collections of data that can be used with the  `[Theory]` attribute.
 - This is good replace for using `IEnumerable<object[]>` for complex data sets.
+- Advantages of using `TheoryData` over `IEnumerable<object[]>`:
+  - **Type Safety**: Since `TheoryData` is strongly typed, it helps catch type-related errors at compile time rather than at runtime.
+  - **Readability**: The structure of `TheoryData` makes it easier to understand the data being provided to the test methods.
+  - **Intellisense Support**: When using `TheoryData`, you get better IntelliSense support in IDEs, making it easier to work with the data.
 
+### MemberData with TheoryData
 ```csharp
 [Theory]
 [MemberData(nameof(GetDistanceTestData))]
@@ -28,3 +33,54 @@ public static TheoryData<Point2D, Point2D, double> GetDistanceTestData()
 }
 ```
 
+```csharp
+public class Point2DTest
+{
+    [Theory]
+    [MemberData(nameof(TestDataPoint2D.Distance), MemberType = typeof(TestDataPoint2D))]
+    public void TestDistanceTo_WithMemberData(Point2D pointA, Point2D pointB, double expectedDistance)
+    {
+        //Act
+        var distance = pointA.DistanceTo(pointB);
+        //Assert
+        Assert.Equal(expectedDistance, distance, 3);
+    }
+}
+public static class TestDataPoint2D
+{
+    public static TheoryData<Point2D, Point2D, double> Distance()
+    {
+        var data = new TheoryData<Point2D, Point2D, double>();
+        data.Add(new Point2D(0, 0), new Point2D(10, 0), 10);
+        data.Add(new Point2D(0, 0), new Point2D(10, 10), 14.1421);
+        data.Add(new Point2D(1, 2), new Point2D(3, 4), 2.8284);
+        return data;
+    }
+}
+```
+
+### ClassData with TheoryData
+```csharp
+public class Point2DTest
+{
+    [Theory]
+    [ClassData(typeof(DistanceTestData))]
+    public void TestDistanceTo_WithMemberData(Point2D pointA, Point2D pointB, double expectedDistance)
+    {
+        //Act
+        var distance = pointA.DistanceTo(pointB);
+        //Assert
+        Assert.Equal(expectedDistance, distance, 3);
+    }
+}
+
+public class DistanceTestData : TheoryData<Point2D, Point2D, double>
+{
+    public DistanceTestData()
+    {
+        Add(new Point2D(0, 0), new Point2D(3, 4), 5.0);
+        Add(new Point2D(1, 1), new Point2D(4, 5), 5.0);
+        Add(new Point2D(-1, -1), new Point2D(2, 3), 5.0);
+    }
+}
+```