diff --git a/LightweightIocContainer/Exceptions/MultipleRegistrationException.cs b/LightweightIocContainer/Exceptions/MultipleRegistrationException.cs
new file mode 100644
index 0000000..2b7eba0
--- /dev/null
+++ b/LightweightIocContainer/Exceptions/MultipleRegistrationException.cs
@@ -0,0 +1,26 @@
+// // Author: Gockner, Simon
+// // Created: 2019-06-07
+// // Copyright(c) 2019 SimonG. All Rights Reserved.
+
+using System;
+using LightweightIocContainer.Interfaces;
+
+namespace LightweightIocContainer.Exceptions
+{
+    /// <summary>
+    /// The Type is already registered in this <see cref="IIocContainer"/>
+    /// </summary>
+    public class MultipleRegistrationException : Exception
+    {
+        public MultipleRegistrationException(Type type)
+            : base($"Type {type.Name} is already registered in this IocContainer.")
+        {
+            Type = type;
+        }
+
+        /// <summary>
+        /// The registered Type
+        /// </summary>
+        public Type Type { get; }
+    }
+}
\ No newline at end of file
diff --git a/LightweightIocContainer/Interfaces/IIocContainer.cs b/LightweightIocContainer/Interfaces/IIocContainer.cs
index 27dcf31..498d2cc 100644
--- a/LightweightIocContainer/Interfaces/IIocContainer.cs
+++ b/LightweightIocContainer/Interfaces/IIocContainer.cs
@@ -3,6 +3,7 @@
 // Copyright(c) 2019 SimonG. All Rights Reserved.
 
 using System;
+using LightweightIocContainer.Exceptions;
 using LightweightIocContainer.Interfaces.Registrations;
 
 namespace LightweightIocContainer.Interfaces
@@ -23,6 +24,7 @@ namespace LightweightIocContainer.Interfaces
         /// Add the <see cref="IRegistrationBase"/> to the the <see cref="IIocContainer"/>
         /// </summary>
         /// <param name="registration">The given <see cref="IRegistrationBase"/></param>
+        /// <exception cref="MultipleRegistrationException">The Type is already registered in this <see cref="IIocContainer"/></exception>
         void Register(IRegistrationBase registration);
 
         /// <summary>
@@ -46,6 +48,7 @@ namespace LightweightIocContainer.Interfaces
         /// <param name="type">The given type</param>
         /// <param name="arguments">The constructor arguments</param>
         /// <returns>An instance of the given type</returns>
+        /// <exception cref="InternalResolveException">Could not find function <see cref="IocContainer.ResolveInternal{T}"/></exception>
         object Resolve(Type type, object[] arguments);
     }
 }
\ No newline at end of file
diff --git a/LightweightIocContainer/IocContainer.cs b/LightweightIocContainer/IocContainer.cs
index f40cadb..e1378f2 100644
--- a/LightweightIocContainer/IocContainer.cs
+++ b/LightweightIocContainer/IocContainer.cs
@@ -39,8 +39,13 @@ namespace LightweightIocContainer
         /// Add the <see cref="IRegistrationBase"/> to the the <see cref="IocContainer"/>
         /// </summary>
         /// <param name="registration">The given <see cref="IRegistrationBase"/></param>
+        /// <exception cref="MultipleRegistrationException">The Type is already registered in this <see cref="IocContainer"/></exception>
         public void Register(IRegistrationBase registration)
         {
+            //if type is already registered
+            if (_registrations.Any(r => r.InterfaceType == registration.InterfaceType))
+                throw new MultipleRegistrationException(registration.InterfaceType);
+
             _registrations.Add(registration);
         }
 
diff --git a/LightweightIocContainer/LightweightIocContainer.csproj b/LightweightIocContainer/LightweightIocContainer.csproj
index bdd66f8..b49c198 100644
--- a/LightweightIocContainer/LightweightIocContainer.csproj
+++ b/LightweightIocContainer/LightweightIocContainer.csproj
@@ -10,7 +10,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Folder Include="Exceptions\" />
     <Folder Include="Factories\" />
     <Folder Include="Interfaces\Factories\" />
     <Folder Include="Interfaces\Registrations\" />