Add -NoHeader parameter to ConvertTo-Csv and Export-Csv cmdlets (#19108)

test/powershell/Modules/Microsoft.PowerShell.Utility/ConvertTo-Csv.Tests.ps1

@@ -91,6 +91,11 @@ Describe "ConvertTo-Csv" -Tags "CI" {
         $result | Should -Not -Match ([regex]::Escape('#TYPE'))
     }
 
+    It "Does not include headers with -NoHeader" {
+        $result = $testObject | ConvertTo-Csv -NoHeader
+        $result | Should -BeExactly '"Hello","World"'
+    }
+
     It "Does not support -UseQuotes and -QuoteFields at the same time" {
         { $testObject | ConvertTo-Csv -UseQuotes Always -QuoteFields "TestFieldName" } |
             Should -Throw -ErrorId "CannotSpecifyQuoteFieldsAndUseQuotes,Microsoft.PowerShell.Commands.ConvertToCsvCommand"

test/powershell/Modules/Microsoft.PowerShell.Utility/Export-Csv.Tests.ps1

@@ -68,6 +68,21 @@ Describe "Export-Csv" -Tags "CI" {
         $results[0] | Should -Not -Match ([regex]::Escape("#TYPE"))
     }
 
+    It "Does not include headers with -NoHeader when exported and can imported with headers" {
+        $P1 | Export-Csv -Path $testCsv -NoHeader
+        $results = Get-Content -Path $testCsv
+        $results | Should -BeExactly '"first"'
+        $results = Import-Csv -Path $testCsv -Header "P1"
+        $results[0].P1 | Should -BeExactly "first"
+    }
+
+    It "Does not include headers when imported with headers and exported using -NoHeader" {
+        $P1 | Export-Csv -Path $testCsv
+        (Import-Csv -Path $testCsv) | Export-Csv -Path $testCsv -NoHeader
+        $results = Get-Content -Path $testCsv
+        $results | Should -BeExactly '"first"'
+    }
+
     It "Includes type information when -IncludeTypeInformation is supplied" {
         $testObject | Export-Csv -Path $testCsv -IncludeTypeInformation
         $results = Get-Content -Path $testCsv