From c648c8116eabb31882c49c44810b4f078a86d9ad Mon Sep 17 00:00:00 2001
From: Shay Rojansky <roji@roji.org>
Date: Sun, 5 Oct 2025 21:45:13 +0200
Subject: [PATCH] Add implicit cast from .NET IPNetwork to NpgsqlInet

Helps EFCore.PG especially, continues #5821.
---
 .../Converters/Networking/IPNetworkConverter.cs     | 13 +++++++++++--
 src/Npgsql/NpgsqlTypes/NpgsqlTypes.cs               |  7 +++++++
 src/Npgsql/PublicAPI.Unshipped.txt                  |  1 +
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/Npgsql/Internal/Converters/Networking/IPNetworkConverter.cs b/src/Npgsql/Internal/Converters/Networking/IPNetworkConverter.cs
index 77714edf29..6fc7b5401e 100644
--- a/src/Npgsql/Internal/Converters/Networking/IPNetworkConverter.cs
+++ b/src/Npgsql/Internal/Converters/Networking/IPNetworkConverter.cs
@@ -1,4 +1,5 @@
-using System.Net;
+using System;
+using System.Net;
 
 // ReSharper disable once CheckNamespace
 namespace Npgsql.Internal.Converters;
@@ -18,5 +19,13 @@ protected override IPNetwork ReadCore(PgReader reader)
     }
 
     protected override void WriteCore(PgWriter writer, IPNetwork value)
-        => NpgsqlInetConverter.WriteImpl(writer, (value.BaseAddress, (byte)value.PrefixLength), isCidr: true);
+        => NpgsqlInetConverter.WriteImpl(
+            writer,
+            (
+                value.BaseAddress,
+                value.PrefixLength <= byte.MaxValue
+                    ? (byte)value.PrefixLength
+                    : throw new ArgumentOutOfRangeException(nameof(value), "IPNetwork.PrefixLength is too large to fit in a byte")
+            ),
+            isCidr: true);
 }
diff --git a/src/Npgsql/NpgsqlTypes/NpgsqlTypes.cs b/src/Npgsql/NpgsqlTypes/NpgsqlTypes.cs
index 7d5eedf7af..4736ca00ec 100644
--- a/src/Npgsql/NpgsqlTypes/NpgsqlTypes.cs
+++ b/src/Npgsql/NpgsqlTypes/NpgsqlTypes.cs
@@ -469,6 +469,13 @@ public static explicit operator IPAddress(NpgsqlInet inet)
     public static implicit operator NpgsqlInet(IPAddress ip)
         => new(ip);
 
+    public static implicit operator NpgsqlInet(IPNetwork cidr)
+        => new(
+            cidr.BaseAddress,
+            cidr.PrefixLength <= byte.MaxValue
+                ? (byte)cidr.PrefixLength
+                : throw new ArgumentOutOfRangeException(nameof(cidr), "IPNetwork.PrefixLength is too large to fit in a byte"));
+
     public void Deconstruct(out IPAddress address, out byte netmask)
     {
         address = Address;
diff --git a/src/Npgsql/PublicAPI.Unshipped.txt b/src/Npgsql/PublicAPI.Unshipped.txt
index a1d261ead0..a0a2c14d56 100644
--- a/src/Npgsql/PublicAPI.Unshipped.txt
+++ b/src/Npgsql/PublicAPI.Unshipped.txt
@@ -84,4 +84,5 @@ Npgsql.NpgsqlConnection.ReloadTypesAsync(System.Threading.CancellationToken canc
 *REMOVED*Npgsql.NpgsqlSlimDataSourceBuilder.MapComposite<T>(string? pgName = null, Npgsql.INpgsqlNameTranslator? nameTranslator = null) -> Npgsql.TypeMapping.INpgsqlTypeMapper!
 *REMOVED*Npgsql.NpgsqlSlimDataSourceBuilder.MapEnum(System.Type! clrType, string? pgName = null, Npgsql.INpgsqlNameTranslator? nameTranslator = null) -> Npgsql.TypeMapping.INpgsqlTypeMapper!
 *REMOVED*Npgsql.NpgsqlSlimDataSourceBuilder.MapEnum<TEnum>(string? pgName = null, Npgsql.INpgsqlNameTranslator? nameTranslator = null) -> Npgsql.TypeMapping.INpgsqlTypeMapper!
+static NpgsqlTypes.NpgsqlInet.implicit operator NpgsqlTypes.NpgsqlInet(System.Net.IPNetwork cidr) -> NpgsqlTypes.NpgsqlInet
 static readonly NpgsqlTypes.NpgsqlTsVector.Empty -> NpgsqlTypes.NpgsqlTsVector!