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

Author: DavidBoone

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

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 
@@ -46,6 +46,12 @@ 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(16)
     {
         {"System.Int16", "short"},
@@ -115,6 +121,19 @@ public static string ToType(this Type type, CodeLanguage language = CodeLanguage
     {
         ArgumentNullException.ThrowIfNull(type);
 
+        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 ?? type.Name, language);
     }
 
@@ -128,34 +147,26 @@ public static string ToType(this string type, CodeLanguage language = CodeLangua
         if (language == CodeLanguage.CSharp && _csharpTypeAlias.TryGetValue(type, out var t))
             return t;
 
-        // drop system from namespace
-        var 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);
-    }
-
-    public static string? ToNullableType(this string? type, bool isNullable = false, CodeLanguage language = CodeLanguage.CSharp)
-    {
-        if (string.IsNullOrEmpty(type))
-            return null;
-
-        bool isValueType = type.IsValueType();
+        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 + "?";
+            : typeString + "?";
     }
 
     public static bool IsValueType(this string? type)