Added -CaseInsensitive switch parameter to Select-Object & Get-Unique cmdlets

src/Microsoft.PowerShell.Commands.Utility/commands/utility/GetUnique.cs

@@ -50,6 +50,13 @@ public SwitchParameter OnType
         }
 
         private bool _onType = false;
+
+        /// <summary>
+        /// Gets or sets case insensitive switch for string comparison.
+        /// </summary>
+        [Parameter]
+        public SwitchParameter CaseInsensitive { get; set; }
+
         #endregion Parameters
 
         #region Overrides
@@ -77,7 +84,7 @@ protected override void ProcessRecord()
                 if (string.Equals(
                     inputString,
                     _lastObjectAsString,
-                    StringComparison.CurrentCulture))
+                    CaseInsensitive.IsPresent ? StringComparison.CurrentCultureIgnoreCase : StringComparison.CurrentCulture))
                 {
                     isUnique = false;
                 }
@@ -89,9 +96,9 @@ protected override void ProcessRecord()
             else // compare as objects
             {
                 _comparer ??= new ObjectCommandComparer(
-                    true, // ascending (doesn't matter)
+                    ascending: true,
                     CultureInfo.CurrentCulture,
-                    true); // case-sensitive
+                    caseSensitive: !CaseInsensitive.IsPresent);
 
                 isUnique = (_comparer.Compare(InputObject, _lastObject) != 0);
             }

src/Microsoft.PowerShell.Commands.Utility/commands/utility/Select-Object.cs

@@ -110,6 +110,13 @@ public SwitchParameter Unique
 
         private bool _unique;
 
+        /// <summary>
+        /// Gets or sets case insensitive switch for string comparison.
+        /// Used in combination with Unique switch parameter.
+        /// </summary>
+        [Parameter]
+        public SwitchParameter CaseInsensitive { get; set; }
+
         /// <summary>
         /// </summary>
         /// <value></value>
@@ -632,7 +639,11 @@ private void FilteredWriteObject(PSObject obj, List<PSNoteProperty> addedNotePro
                 bool isObjUnique = true;
                 foreach (UniquePSObjectHelper uniqueObj in _uniques)
                 {
-                    ObjectCommandComparer comparer = new(true, CultureInfo.CurrentCulture, true);
+                    ObjectCommandComparer comparer = new(
+                        ascending: true,
+                        CultureInfo.CurrentCulture,
+                        caseSensitive: !CaseInsensitive.IsPresent);
+
                     if ((comparer.Compare(obj.BaseObject, uniqueObj.WrittenObject.BaseObject) == 0) &&
                         (uniqueObj.NotePropertyCount == addedNoteProperties.Count))
                     {

test/powershell/Modules/Microsoft.PowerShell.Utility/Get-Unique.Tests.ps1

@@ -1,8 +1,12 @@
 # Copyright (c) Microsoft Corporation.
 # Licensed under the MIT License.
 Describe "Get-Unique DRT Unit Tests" -Tags "CI" {
-    It "Command get-unique works with AsString switch" {
+
+    BeforeAll {
         $inputArray = "aa","aa","Aa","ba","BA","BA"
+    }
+
+    It "Command get-unique works with AsString switch" {
         $results = $inputArray | Get-Unique -AsString
 
         $results.Length | Should -Be 4
@@ -17,6 +21,18 @@ Describe "Get-Unique DRT Unit Tests" -Tags "CI" {
         $results[2] | Should -BeOfType System.String
         $results[3] | Should -BeOfType System.String
     }
+
+    It "Command get-unique works with AsString and CaseInsensitive switches" {
+        $results = $inputArray | Get-Unique -AsString -CaseInsensitive
+
+        $results.Length | Should -Be 2
+
+        $results[0] | Should -BeExactly "aa"
+        $results[1] | Should -BeExactly "ba"
+
+        $results[0] | Should -BeOfType System.String
+        $results[1] | Should -BeOfType System.String
+    }
 }
 
 Describe "Get-Unique" -Tags "CI" {
@@ -26,6 +42,8 @@ Describe "Get-Unique" -Tags "CI" {
         $expectedOutput1 = 1,2,3,4,5
         $collection     = "a", "b", "b", "d"
         $expectedOutput2 = "a", "b", "d"
+        $collection2 = "a","A", "b", "B"
+        $expectedOutput3 = "a", "b"
     }
 
     It "Should be able to use the Get-Unique cmdlet without error with inputObject switch" {
@@ -61,4 +79,9 @@ Describe "Get-Unique" -Tags "CI" {
         $actual = $collection | Get-Unique
         $(Compare-Object $actual $expectedOutput2 -SyncWindow 0).Length | Should -Be 0
     }
+
+    It "Should get the unique strings when CaseInsensitive switch is used" {
+        $actual = $collection2 | Get-Unique -CaseInsensitive
+        $(Compare-Object $actual $expectedOutput3 -SyncWindow 0).Length | Should -Be 0
+    }
 }

test/powershell/Modules/Microsoft.PowerShell.Utility/Select-Object.Tests.ps1

@@ -58,6 +58,13 @@ Describe "Select-Object" -Tags "CI" {
         $result | Should -Be $expected
     }
 
+    It "Should work work correctly with Unique and CaseInsensitive parameter" {
+        $result = "abc", "Abc" | Select-Object -Unique -CaseInsensitive
+
+        $result.Count | Should -Be 1
+        $result | Should -Be "abc"
+    }
+
     It "Should return correct object with Skip parameter" {
         $result = $dirObject | Select-Object -Skip $TestLength