diff --git a/src/Uno.CodeGen.Tests.ExternalClasses/ConcreteExternalGenericClass.cs b/src/Uno.CodeGen.Tests.ExternalClasses/ConcreteExternalGenericClass.cs
new file mode 100644
index 0000000..2c9cd1e
--- /dev/null
+++ b/src/Uno.CodeGen.Tests.ExternalClasses/ConcreteExternalGenericClass.cs
@@ -0,0 +1,25 @@
+// ******************************************************************
+// Copyright � 2015-2018 nventive inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// ******************************************************************
+namespace Uno.CodeGen.Tests.ExternalClasses
+{
+	[GeneratedImmutable]
+	public abstract partial class ConcreteExternalGenericClass<TId>
+	{
+		[EqualityHash]
+		public TId Id { get; }
+	}
+}
diff --git a/src/Uno.CodeGen.Tests.ExternalClasses/SubNamespace/ConcreteExternalClass.cs b/src/Uno.CodeGen.Tests.ExternalClasses/SubNamespace/ConcreteExternalClass.cs
new file mode 100644
index 0000000..8328f34
--- /dev/null
+++ b/src/Uno.CodeGen.Tests.ExternalClasses/SubNamespace/ConcreteExternalClass.cs
@@ -0,0 +1,25 @@
+// ******************************************************************
+// Copyright � 2015-2018 nventive inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// ******************************************************************
+namespace Uno.CodeGen.Tests.ExternalClasses.SubNamespace
+{
+	[GeneratedImmutable]
+	public partial class ConcreteExternalClass
+	{
+		[EqualityHash]
+		public string Id { get; }
+	}
+}
diff --git a/src/Uno.CodeGen.Tests.ExternalClasses/SubNamespace/ConcreteExternalGenericClass.cs b/src/Uno.CodeGen.Tests.ExternalClasses/SubNamespace/ConcreteExternalGenericClass.cs
new file mode 100644
index 0000000..af48c65
--- /dev/null
+++ b/src/Uno.CodeGen.Tests.ExternalClasses/SubNamespace/ConcreteExternalGenericClass.cs
@@ -0,0 +1,25 @@
+// ******************************************************************
+// Copyright � 2015-2018 nventive inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// ******************************************************************
+namespace Uno.CodeGen.Tests.ExternalClasses.SubNamespace
+{
+	[GeneratedImmutable]
+	public abstract partial class ConcreteExternalGenericClass<TId>
+	{
+		[EqualityHash]
+		public TId Id { get; }
+	}
+}
diff --git a/src/Uno.CodeGen/Helpers/NamedTypeSymbolExtensions.cs b/src/Uno.CodeGen/Helpers/NamedTypeSymbolExtensions.cs
index ca862ce..9b93115 100644
--- a/src/Uno.CodeGen/Helpers/NamedTypeSymbolExtensions.cs
+++ b/src/Uno.CodeGen/Helpers/NamedTypeSymbolExtensions.cs
@@ -31,9 +31,13 @@ namespace Uno.Helpers
 			var substitutions = typeToUseForSubstitutions.GetSubstitutionTypes();
 
 			var symbolName = typeSymbol.Name;
+
+			// Generate a filename suffix from the namespace to prevent filename clashing when processing classes with the same name.
+			var filenameSuffix = $"{typeSymbol.GetNamespaceHash():X}";
+
 			if (typeSymbol.TypeArguments.Length == 0) // not a generic type
 			{
-				return new SymbolNames(typeSymbol, symbolName, "", symbolName, symbolName, symbolName, symbolName, "");
+				return new SymbolNames(typeSymbol, symbolName, "", symbolName, symbolName, symbolName, $"{symbolName}_{filenameSuffix}", "");
 			}
 
 			var argumentNames = typeSymbol.GetTypeArgumentNames(substitutions);
@@ -49,7 +53,7 @@ namespace Uno.Helpers
 			var symbolNameDefinition = $"{symbolName}<{string.Join(",", typeSymbol.TypeArguments.Select(ta => ""))}>";
 
 			// symbolNameWithGenerics: MyType_T1_T2
-			var symbolFilename = $"{symbolName}_{string.Join("_", argumentNames)}";
+			var symbolFilename = $"{symbolName}_{string.Join("_", argumentNames)}_{filenameSuffix}";
 
 			var genericConstraints = " " + string.Join(" ", typeSymbol
 				.TypeArguments
@@ -98,6 +102,19 @@ namespace Uno.Helpers
 
 			return result;
 		}
+
+		public static int GetNamespaceHash(this INamedTypeSymbol typeSymbol)
+		{
+			var hashCode = 0;
+			INamespaceSymbol namespaceSymbol = typeSymbol.ContainingNamespace;
+			while (!namespaceSymbol?.IsGlobalNamespace ?? false)
+			{
+				hashCode ^= namespaceSymbol.Name.GetStableHashCode();
+				namespaceSymbol = namespaceSymbol.ContainingNamespace;
+			}
+
+			return hashCode;
+		}
 	}
 
 	public class SymbolNames
diff --git a/src/Uno.CodeGen/Helpers/StringExtensions.cs b/src/Uno.CodeGen/Helpers/StringExtensions.cs
new file mode 100644
index 0000000..c169fa3
--- /dev/null
+++ b/src/Uno.CodeGen/Helpers/StringExtensions.cs
@@ -0,0 +1,51 @@
+// ******************************************************************
+// Copyright � 2015-2018 nventive inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// ******************************************************************
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Reflection;
+using Microsoft.CodeAnalysis;
+
+namespace Uno.Helpers
+{
+	public static class StringExtensions
+	{
+		public static int GetStableHashCode(this string str)
+		{
+			// A fully managed version of the 64bit GetHashCode() that does not use any randomization and will always return
+			// the same value for equal strings.
+			// https://stackoverflow.com/questions/36845430/persistent-hashcode-for-strings
+			unchecked
+			{
+				int hash1 = 5381;
+				int hash2 = hash1;
+
+				for (int i = 0; i < str.Length && str[i] != '\0'; i += 2)
+				{
+					hash1 = ((hash1 << 5) + hash1) ^ str[i];
+					if (i == str.Length - 1 || str[i + 1] == '\0')
+						break;
+					hash2 = ((hash2 << 5) + hash2) ^ str[i + 1];
+				}
+
+				return hash1 + (hash2 * 1566083941);
+			}
+		}
+	}
+}