Handle omitted data content type in Set-CloudEventData

src/CloudEventsPowerShell/CloudEvents.Sdk.psm1

@@ -146,13 +146,16 @@ function Set-CloudEventData {
 
     PROCESS {
 
-        # https://github.com/cloudevents/spec/blob/main/cloudevents/spec.md#datacontenttype
-        $contentType = New-Object `
-            -TypeName 'System.Net.Mime.ContentType' `
-            -ArgumentList ($DataContentType)
-
         $cloudEvent.Data = $Data
-        $cloudEvent.DataContentType = $dataContentType
+
+        if ($PSBoundParameters.ContainsKey('DataContentType')) {
+            # https://github.com/cloudevents/spec/blob/main/cloudevents/spec.md#datacontenttype
+            $contentType = New-Object `
+                -TypeName 'System.Net.Mime.ContentType' `
+                -ArgumentList ($DataContentType)
+
+            $cloudEvent.DataContentType = $contentType
+        }
 
         if ($PSBoundParameters.ContainsKey('DataSchema')) {
             $cloudEvent.DataSchema = $DataSchema

test/unit/Set-CloudEventData.Tests.ps1

@@ -25,10 +25,20 @@ Describe "Set-CloudEventData Function Tests" {
          # Assert
          $actual | Should -Not -Be $null
          $actual.DataContentType.ToString() | Should -Be $expectedDataContentType
+         $actual.DataContentType | Should -BeOfType ([System.Net.Mime.ContentType])
          $actual.Data | Should -Be $expectedData
          $actual.DataSchema | Should -BeNullOrEmpty
       }
 
+      It 'Sets data when DataContentType is omitted' {
+         $cloudEvent = New-CloudEvent -Id 'test-id' -Type test -Source 'urn:test'
+
+         $actual = $cloudEvent | Set-CloudEventData -Data 'test'
+
+         $actual.Data | Should -Be 'test'
+         $actual.DataContentType | Should -BeNullOrEmpty
+      }
+
       It 'Sets xml text data' {
          # Arrange
          $cloudEvent = New-CloudEvent `