Add documentation for NU1016 error code (project.json deprecation) (#3469)

Author: Copilot

docs/reference/Errors-and-Warnings.md

@@ -27,7 +27,7 @@ NuGet supports the following configuration properties.
 
 | Group | Error Numbers |
 | --- | --- |
-| Invalid input errors | [NU1001](./errors-and-warnings/NU1001.md), [NU1002](./errors-and-warnings/NU1002.md), [NU1003](./errors-and-warnings/NU1003.md), [NU1004](./errors-and-warnings/NU1004.md), [NU1005](./errors-and-warnings/NU1005.md), [NU1006](./errors-and-warnings/NU1006.md), [NU1007](./errors-and-warnings/NU1007.md), [NU1008](./errors-and-warnings/NU1008.md), [NU1009](./errors-and-warnings/NU1009.md), [NU1010](./errors-and-warnings/NU1010.md), [NU1011](./errors-and-warnings/NU1011.md), [NU1012](./errors-and-warnings/NU1012.md), [NU1013](./errors-and-warnings/NU1013.md), [NU1014](./errors-and-warnings/NU1014.md), [NU1015](./errors-and-warnings/NU1015.md) |
+| Invalid input errors | [NU1001](./errors-and-warnings/NU1001.md), [NU1002](./errors-and-warnings/NU1002.md), [NU1003](./errors-and-warnings/NU1003.md), [NU1004](./errors-and-warnings/NU1004.md), [NU1005](./errors-and-warnings/NU1005.md), [NU1006](./errors-and-warnings/NU1006.md), [NU1007](./errors-and-warnings/NU1007.md), [NU1008](./errors-and-warnings/NU1008.md), [NU1009](./errors-and-warnings/NU1009.md), [NU1010](./errors-and-warnings/NU1010.md), [NU1011](./errors-and-warnings/NU1011.md), [NU1012](./errors-and-warnings/NU1012.md), [NU1013](./errors-and-warnings/NU1013.md), [NU1014](./errors-and-warnings/NU1014.md), [NU1015](./errors-and-warnings/NU1015.md), [NU1016](./errors-and-warnings/NU1016.md) |
 | Missing package and project errors | [NU1100](./errors-and-warnings/NU1100.md), [NU1101](./errors-and-warnings/NU1101.md), [NU1102](./errors-and-warnings/NU1102.md), [NU1103](./errors-and-warnings/NU1103.md), [NU1104](./errors-and-warnings/NU1104.md), [NU1105](./errors-and-warnings/NU1105.md), [NU1106](./errors-and-warnings/NU1106.md), [NU1107](./errors-and-warnings/NU1107.md), [NU1108](./errors-and-warnings/NU1108.md), [NU1109](./errors-and-warnings/NU1109.md) |
 | Package source mapping errors | [NU1110](./errors-and-warnings/NU1110.md) |
 | Compatibility errors | [NU1201](./errors-and-warnings/NU1201.md), [NU1202](./errors-and-warnings/NU1202.md), [NU1203](./errors-and-warnings/NU1203.md), [NU1204](./errors-and-warnings/NU1204.md), [NU1401](./errors-and-warnings/NU1401.md), [NU1402](./errors-and-warnings/NU1402.md), [NU1403](./errors-and-warnings/NU1403.md) |

docs/reference/errors-and-warnings/NU1016.md

@@ -0,0 +1,34 @@
+---
+title: NuGet Error NU1016
+description: NU1016 error code
+author: donnie-msft
+ms.author: eagoodso
+ms.date: 01/28/2025
+ms.topic: reference
+f1_keywords: 
+  - "NU1016"
+---
+
+# NuGet Error NU1016
+
+> Managing packages with project.json is deprecated. Migrate to PackageReference.
+
+### Issue
+
+Managing packages with project.json is deprecated. Migrate to PackageReference.
+
+### Solution
+
+[Migrate your project from project.json to PackageReference](../../archive/project-json.md#migrate-projectjson-to-packagereference).
+
+In Visual Studio 2026 or newer, your project.json project will be automatically migrated.
+
+In Visual Studio 2022, you need to use the [built-in migrator](../../archive/project-json.md#migrate-projectjson-to-packagereference).
+
+1. Open your project.json project in Visual Studio
+1. In Solution Explorer, find the project's Dependencies node
+1. Right-click and select **Migrate project.json to PackageReference...**
+
+For detailed migration guidance, see the [project.json reference documentation](../../archive/project-json.md).
+
+For more information about package management formats, see [Package references in project files](../../consume-packages/Package-References-in-Project-Files.md).