- add invalid and missing key exception

GBase/Exceptions/InvalidKeyException.cs

@@ -0,0 +1,17 @@
+// Author: Gockner, Simon
+// Created: 2020-11-13
+// Copyright(c) 2020 SimonG. All Rights Reserved.
+
+using System;
+
+namespace GBase.Exceptions
+{
+    public class InvalidKeyException : Exception
+    {
+        public InvalidKeyException(string message)
+            : base(message)
+        {
+            
+        }
+    }
+}

GBase/Exceptions/MissingKeyColumnException.cs

@@ -0,0 +1,17 @@
+// Author: Gockner, Simon
+// Created: 2020-11-13
+// Copyright(c) 2020 SimonG. All Rights Reserved.
+
+using System;
+
+namespace GBase.Exceptions
+{
+    public class MissingKeyColumnException<T> : Exception
+    {
+        public MissingKeyColumnException()
+            : base($"Type {typeof(T)} is missing a key column.")
+        {
+            
+        }
+    }
+}