Add NU1704 warning documentation for deprecated MonoAndroid framework

Author: sbomer

docs/reference/Errors-and-Warnings.md

@@ -46,7 +46,7 @@ NuGet supports the following configuration properties.
 | Invalid input warnings | [NU1501](./errors-and-warnings/NU1501.md), [NU1502](./errors-and-warnings/NU1502.md), [NU1503](./errors-and-warnings/NU1503.md), [NU1504](./errors-and-warnings/NU1504.md), [NU1505](./errors-and-warnings/NU1505.md), [NU1506](./errors-and-warnings/NU1506.md), [NU1507](./errors-and-warnings/NU1507.md), [NU1508](./errors-and-warnings/NU1508.md), [NU1509](./errors-and-warnings/NU1509.md), [NU1510](./errors-and-warnings/NU1510.md), [NU1511](./errors-and-warnings/NU1511.md) |
 | Unexpected package version warnings | [NU1601](./errors-and-warnings/NU1601.md), [NU1602](./errors-and-warnings/NU1602.md), [NU1603](./errors-and-warnings/NU1603.md), [NU1604](./errors-and-warnings/NU1604.md), [NU1605](./errors-and-warnings/NU1605.md), [NU1606](./errors-and-warnings/NU1108.md), [NU1607](./errors-and-warnings/NU1107.md) |
 | Resolver conflict warnings | [NU1608](./errors-and-warnings/NU1608.md) |
-| Package fallback warnings | [NU1701](./errors-and-warnings/NU1701.md), [NU1702](./errors-and-warnings/NU1702.md), [NU1703](./errors-and-warnings/NU1703.md)|
+| Package fallback warnings | [NU1701](./errors-and-warnings/NU1701.md), [NU1702](./errors-and-warnings/NU1702.md), [NU1703](./errors-and-warnings/NU1703.md), [NU1704](./errors-and-warnings/NU1704.md) |
 | Feed warnings | [NU1801](./errors-and-warnings/NU1801.md), [NU1802](./errors-and-warnings/NU1802.md), [NU1803](./errors-and-warnings/NU1803.md) |
 | NuGet internal warnings | [NU1500](./errors-and-warnings/NU1500.md) |
 | Signed packages warnings (creation and verification) | [NU3000](./errors-and-warnings/NU3000.md), [NU3002](./errors-and-warnings/NU3002.md), [NU3003](./errors-and-warnings/NU3003.md), [NU3006](./errors-and-warnings/NU3006.md), [NU3007](./errors-and-warnings/NU3007.md), [NU3009](./errors-and-warnings/NU3009.md), [NU3010](./errors-and-warnings/NU3010.md), [NU3011](./errors-and-warnings/NU3011.md), [NU3012](./errors-and-warnings/NU3012.md), [NU3013](./errors-and-warnings/NU3013.md), [NU3014](./errors-and-warnings/NU3014.md), [NU3015](./errors-and-warnings/NU3015.md), [NU3016](./errors-and-warnings/NU3016.md), [NU3017](./errors-and-warnings/NU3017.md), [NU3018](./errors-and-warnings/NU3018.md), [NU3019](./errors-and-warnings/NU3019.md), [NU3020](./errors-and-warnings/NU3020.md), [NU3021](./errors-and-warnings/NU3021.md), [NU3022](./errors-and-warnings/NU3022.md), [NU3023](./errors-and-warnings/NU3023.md), [NU3024](./errors-and-warnings/NU3024.md), [NU3025](./errors-and-warnings/NU3025.md), [NU3026](./errors-and-warnings/NU3026.md), [NU3027](./errors-and-warnings/NU3027.md), [NU3028](./errors-and-warnings/NU3028.md), [NU3029](./errors-and-warnings/NU3029.md), [NU3030](./errors-and-warnings/NU3030.md), [NU3031](./errors-and-warnings/NU3031.md), [NU3032](./errors-and-warnings/NU3032.md), [NU3033](./errors-and-warnings/NU3033.md), [NU3035](./errors-and-warnings/NU3035.md), [NU3036](./errors-and-warnings/NU3036.md), [NU3037](./errors-and-warnings/NU3037.md), [NU3038](./errors-and-warnings/NU3038.md), [NU3040](./errors-and-warnings/NU3040.md), [NU3042](./errors-and-warnings/NU3042.md), [NU3043](./errors-and-warnings/NU3043.md) |

docs/reference/errors-and-warnings/NU1704.md

@@ -0,0 +1,34 @@
+---
+title: NuGet Warning NU1704
+description: NU1704 warning code
+author: sbomer
+ms.date: 03/25/2026
+ms.topic: reference
+f1_keywords:
+  - "NU1704"
+---
+
+# NuGet Warning NU1704
+
+> Package 'Xamarin.Essentials' 1.8.1 uses the deprecated MonoAndroid framework instead of 'net6.0-android' or later. Consider upgrading to a newer version of this package or contacting the package author.
+
+### Issue
+
+A project targeting `net11.0-android` or later references a package whose resolved compile-time or runtime assemblies come from a `monoandroid` framework folder. The `MonoAndroid` target framework is deprecated in favor of `net6.0-android` and later .NET TFMs.
+
+This warning is only raised when both of the following conditions are met:
+
+- The project targets `net11.0-android` or later.
+- The SDK analysis level is 11.0.100 or higher.
+
+### Solution
+
+Upgrade to a newer version of the package that provides `net6.0-android` (or later) assets. If no updated version is available, contact the package author and request they update the package to target modern .NET Android TFMs.
+
+To suppress the warning, add `NU1704` to the `NoWarn` property in your project file:
+
+```xml
+<PropertyGroup>
+  <NoWarn>$(NoWarn);NU1704</NoWarn>
+</PropertyGroup>
+```