Handle Generic types such as List<> and NpgsqlRange<>

Author: DavidBoone

src/EntityFrameworkCore.Generator.Core/Extensions/GenerationExtensions.cs

@@ -43,6 +43,12 @@ public static class GenerationExtensions
         "class_initialize"
     };
 
+    private static readonly List<string> _defaultUsings = new List<string>()
+    {
+        "System.Collections.Generic",
+        "System"
+    };
+
     private static readonly Dictionary<string, string> _csharpTypeAlias = new Dictionary<string, string>(16)
     {
         {"System.Int16", "short"},
@@ -99,6 +105,19 @@ public static string ToSafeName(this string name, CodeLanguage language = CodeLa
 
     public static string ToType(this Type type, CodeLanguage language = CodeLanguage.CSharp)
     {
+        if (type.IsGenericType)
+        {
+            var genericType = type.GetGenericTypeDefinition().FullName
+                .Split('`')[0];     // trim the `1 bit
+
+            genericType = ToType(genericType, language);
+
+            var elementType = ToType(type.GetGenericArguments()[0].FullName, language);
+            return language == CodeLanguage.VisualBasic
+                ? $"{genericType}(Of {elementType})"
+                : $"{genericType}<{elementType}>";
+        }
+
         return ToType(type.FullName, language);
     }
 
@@ -110,40 +129,26 @@ public static string ToType(this string type, CodeLanguage language = CodeLangua
         if (language == CodeLanguage.CSharp && _csharpTypeAlias.TryGetValue(type, out string t))
             return t;
 
-        // drop system from namespace
-        string[] parts = type.Split('.');
-        if (parts.Length == 2 && parts[0] == "System")
-            return parts[1];
+        // drop common namespaces
+        foreach (var defaultUsing in _defaultUsings)
+            if (type.StartsWith(defaultUsing))
+                return type.Remove(0, defaultUsing.Length + 1);
 
         return type;
     }
 
     public static string ToNullableType(this Type type, bool isNullable = false, CodeLanguage language = CodeLanguage.CSharp)
     {
-        return ToNullableType(type.FullName, isNullable, language);
-    }
+        bool isValueType = type.IsValueType;
 
-    public static string ToNullableType(this string type, bool isNullable = false, CodeLanguage language = CodeLanguage.CSharp)
-    {
-        bool isValueType = type.IsValueType();
-
-        type = type.ToType(language);
+        var typeString = type.ToType(language);
 
         if (!isValueType || !isNullable)
-            return type;
+            return typeString;
 
         return language == CodeLanguage.VisualBasic
-            ? $"Nullable(Of {type})"
-            : type + "?";
-    }
-
-    public static bool IsValueType(this string type)
-    {
-        if (!type.StartsWith("System."))
-            return false;
-
-        var t = Type.GetType(type, false);
-        return t != null && t.IsValueType;
+            ? $"Nullable(Of {typeString})"
+            : typeString + "?";
     }
 
     public static string ToLiteral(this string value)