[iOS] Fix for the File.ContentType from MediaPicker not being in valid MIME format (#28842)

* [iOS] Fix for 15562 ( File.ContentType from MediaPicker is not in MIME format ).

* [iOS] Fix for 15562 (File.ContentType from MediaPicker is not in MIME format)

* [iOS] Fix for 15562 (File.ContentType from MediaPicker is not in MIME format)

* [iOS] Fix for 15562 ( File.ContentType from MediaPicker is not in MIME format )

Author: SyedAbdulAzeemSF4852

src/Essentials/src/FileSystem/FileSystem.ios.tvos.watchos.macos.cs

@@ -67,9 +67,12 @@ string PlatformGetContentType(string extension)
 			// ios does not like the extensions
 			extension = extension?.TrimStart('.');
 
-			// var id = UTType.CreatePreferredIdentifier(UTType.TagClassFilenameExtension, extension, null);
-			// var mimeTypes = UTType.CopyAllTags(id, UniformTypeIdentifiers.UTTagClass.MimeType.ToString());
-			// return mimeTypes?.Length > 0 ? mimeTypes[0] : null;
+			// UTType supports only iOS version greater than 14
+			if (OperatingSystem.IsIOSVersionAtLeast(14))
+			{
+				var uti = UniformTypeIdentifiers.UTType.GetType(extension, UniformTypeIdentifiers.UTTagClass.FilenameExtension, null);
+				extension = uti?.PreferredMimeType ?? extension;
+			}
 
 			return extension;
 		}

src/Essentials/test/DeviceTests/Tests/FileSystem_Tests.cs

@@ -43,5 +43,19 @@ public async Task OpenAppPackageFileAsync_Throws_If_File_Is_Not_Found()
 		{
 			await Assert.ThrowsAsync<FileNotFoundException>(() => FileSystem.OpenAppPackageFileAsync("MissingFile.txt")).ConfigureAwait(false);
 		}
+
+#if MACCATALYST
+		[Fact]
+		public async Task ValidateMIMEFormat()
+		{
+			string filePath = Path.Combine(FileSystem.CacheDirectory, "sample.txt");
+			await File.WriteAllTextAsync(filePath, "File Content type is text/plain");
+
+			FileResult fileResult = new FileResult(filePath);
+			Assert.Equal("text/plain", fileResult.ContentType);
+
+			File.Delete(filePath);
+		}
+#endif
 	}
 }