Add NU1015 docs (#3437)

Author: zivkan

docs/TOC.md

@@ -153,6 +153,7 @@
 ### [NU1011](reference/errors-and-warnings/NU1011.md)
 ### [NU1012](reference/errors-and-warnings/NU1012.md)
 ### [NU1014](reference/errors-and-warnings/NU1014.md)
+### [NU1015](reference/errors-and-warnings/NU1015.md)
 ### [NU1100](reference/errors-and-warnings/NU1100.md)
 ### [NU1101](reference/errors-and-warnings/NU1101.md)
 ### [NU1102](reference/errors-and-warnings/NU1102.md)

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), |
+| 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) |
 | 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/NU1015.md

@@ -0,0 +1,34 @@
+---
+title: NuGet Error NU1015
+description: NU1015 error code
+author: zivkan
+ms.author: zivkan
+ms.date: 06/04/2025
+ms.topic: reference
+f1_keywords: 
+  - "NU1015"
+---
+
+# NuGet Error NU1015
+
+## Scenario
+
+> The following PackageReference item(s) do not have a version specified: Contoso.Utilities
+
+### Issue
+
+Your project file, or a file it imports (for example `Directory.Build.props`) has defined a `PackageReference` without a version.
+
+Projects using [Central Package Management (CPM)](../../consume-packages/Central-Package-Management.md) do not define a version on the PackageReference item, so this error could happen if a project has CPM disabled by accident, or if a project or `PackageReference` using CPM is copied into another solution that is not using CPM.
+
+### Solution
+
+- Add a version to the package reference
+
+If you edit your project, a package reference will generally look similar to `<PackageReference Include="Contoso.Utilities" Version="1.2.3" />`, although [MSBuild allows multiple syntaxes to define item metadata](/visualstudio/msbuild/msbuild-items).
+Add the `Version="1.2.3"` item metadata as defined.
+
+- Check Central Package Management configuration
+
+This NU1015 error only happens when CPM is disabled.
+If Central Package Management (CPM) is intended to be enabled, check your configuration files to investigate why it is disabled.