Updates Invoke-MgGraphRequest cmdlet to handle responses of text/plain content types.

src/Authentication/Authentication/Cmdlets/InvokeMgGraphRequest.cs

@@ -453,6 +453,10 @@ internal async Task ProcessResponseAsync(HttpResponseMessage response)
                                 throw new ArgumentOutOfRangeException(nameof(OutputType));
                         }
                         break;
+                    case RestReturnType.PlainText:
+                        responseString = await response.Content.ReadAsStringAsync();
+                        WriteObject(responseString);
+                        break;
                     case RestReturnType.OctetStream:
                         if (OutputType == OutputType.HttpResponseMessage)
                             WriteObject(response);

src/Authentication/Authentication/Helpers/ContentHelper.cs

@@ -29,6 +29,8 @@ internal static RestReturnType CheckReturnType(this HttpResponseMessage response
                 rt = RestReturnType.Image;
             else if (IsOctetStream(contentType))
                 rt = RestReturnType.OctetStream;
+            else if (IsPlainText(contentType))
+                rt = RestReturnType.PlainText;
             return rt;
         }
 
@@ -80,6 +82,8 @@ private static bool CheckIsOctetStream(string contentType)
             return isOctetStream;
         }
 
+        private static bool IsPlainText(string contentType) => contentType.Equals("text/plain", StringComparison.OrdinalIgnoreCase);
+
         // used to split contentType arguments
         private static readonly char[] ContentTypeParamSeparator = { ';' };
 

src/Authentication/Authentication/Models/RestReturnType.cs

@@ -24,6 +24,10 @@ public enum RestReturnType
         /// <summary>
         ///      image/* (image/jpeg, image/png) return type
         /// </summary>
-        Image = 4
+        Image = 4,
+        /// <summary>
+        ///      text/plain return type
+        /// </summary>
+        PlainText = 5
     }
 }

src/Authentication/Authentication/test/Invoke-MgGraphRequest.Tests.ps1

@@ -54,6 +54,9 @@ Describe 'Invoke-MgGraphRequest Command' -skip {
           It 'Should not throw when -InferOutputFilePath is specified' {
                { Invoke-MgGraphRequest -OutputType PSObject -Uri "https://graph.microsoft.com/v1.0/reports/getTeamsUserActivityUserDetail(period='D7')" -InferOutputFileName } | Should -Not -Throw
           }
+          It 'Should return plain text' {
+               { Invoke-MgGraphRequest -Uri "https://graph.microsoft.com/v1.0/applications/`$count" } | Should -BeOfType [System.String]
+          }
      }
 
      Context 'Absolute and relative URIs' {