When you create a NuGet package, you can specify dependencies for the package in the .nuspec file. You also specify which versions of a dependency package are required. For information about creating NuGet packages and the .nuspec file format, see Creating a Package and .nuspec File Format Specification.
Dependency versions are specified in the version attribute of the dependency element. For example, the following dependency element specifies a dependency on version 1.3.2 or higher of the package named ExamplePackage.
Specifying Version Ranges in .nuspec Files
<dependency id="ExamplePackage" version="1.3.2" />
NuGet supports using interval notation for specifying version ranges. The NuGet specification was inspired by the Maven Version Range Specification but is not identical to it. The following summarizes how to specify version ranges.
1.0 = 1.0 ≤ x (,1.0] = x ≤ 1.0 (,1.0) = x < 1.0 [1.0] = x == 1.0 (1.0) = invalid (1.0,) = 1.0 < x (1.0,2.0) = 1.0 < x < 2.0 [1.0,2.0] = 1.0 ≤ x ≤ 2.0
When you fail to specify a package version for a dependency as follows:
<dependency id="ExamplePackage" />
NuGet will perform the following actions:
NuGet v2.7.2 and earlier - the latest package version will be used NuGet v2.8 and greater - the lowest package version will be used
It is recommended to always specify a version or version range for package dependencies.
The following example specifies a dependency on any version of ExamplePackage that begins with a 1 or a 2. The square bracket indicates that the 1 is included, while the parenthesis indicates that 3 is excluded.
<dependency id="ExamplePackage" version="[1,3)" />
In the example, version 1 and version 2.9 would be acceptable, but not 0.9 or 3.0.
The following example specifies a dependency on ExamplePackage 1.3.2 through any version number that begins with 1.4. The square bracket indicates that the 1.3.2 is included, while the parenthesis indicates that 1.5 is excluded.
<dependency id="ExamplePackage" version="[1.3.2,1.5)" />
In the example, version 184.108.40.206 and version 1.4.999 would be acceptable, but not version 1.5.
Generally, the guidance in most cases is to only specify a lower bound, and leave the upper bound open. e.g.
<dependency id="ExamplePackage" version="1.3.2" />
When most people install packages from NuGet, they want the latest “stable” release of that package. Other developers like to live life on the edge and want to grab the latest prerelease version of a package.
As of NuGet 1.6, NuGet supports the creation of prerelease packages by specifying a prerelease string in the version number according to the Semantic Versioning (SemVer) specification v1.0.0.
Really brief introduction to SemVer
The SemVer spec is the best place to get a detailed understanding of SemVer. For those in a hurry, this is a brief rundown of SemVer.
SemVer is a convention for versioning your public APIs in which the version number has meaning attached to it. Each version has three parts, Major.Minor.Patch.
In brief, these correspond to:
- Major: Breaking changes.
- Minor: New features, but backwards compatible.
- Patch: Backwards compatible bug fixes only.
Additionally, prerelease versions of your API can be denoted by appending an arbitrary string to the Patch number separated by a dash. For example:
Note that the actual string applied doesn't matter. If there's a string there, it's a prerelease version.
When you’re ready to release, just remove the dash and the string and that version is considered “higher”
than all the prerelease versions. For example, the stable version
1.0.1 is larger than
The prerelease versions are given precedence in alphabetical order (well technically lexicographic ASCII sort order).
Therefore, the following is an example from lowest to highest versions of a package.
SemVer also introduces the concept of a build number for those creating daily or continuous builds. This is not supported in the public NuGet.org gallery, so while this is allowed:
including the SemVer-compatible build number with dot notation is not allowed:
Creating Prerelease Packages
As mentioned before, to create a prerelease package, simply give it a version that has a prerelease string. There are two ways this can be accomplished.
Within the NuSpec file, specify the version in the <version /> element
If building a package from a project (.csproj or .vbproj), use the
AssemblyInformationalVersionAttributeto specify the version.
NuGet will pick up this value instead of the one specified in the
AssemblyVersion attribute (this
attribute does not support SemVer which is why a different attribute was needed).
Installing Prerelease Packages
By default, NuGet does not display prerelease packages in the dialog or in the console. The Manage NuGet Packages dialog supports the display and installation of prerelease versions via a drop down menu above the package list. Selecting "Include Prelease" rather than the default "Stable Only" will allow you to install these pacakges.
You can also use the Package Manager Console and specify the
-IncludePrerelease flag as follows.
Install-Package CoolStuff -IncludePrerelease
This command includes prerelease packages in the set of packages considered. If a prerelease package is the latest version, then it is installed. If a stable package is the latest, it is installed. This flag does not force a prerelease package to be installed.
You are also free to use the
-Pre alias for installing prerelease packages.
Install-Package CoolStuff -Pre
NuGet does not allow a stable package to reference a prerelease package. This avoids accidentally installing a prerelease package when you're only interested in stable packages.
Upgrading Prerelease Packages
Update-Package command will update all packages to the latest stable version. As before, use the
-IncludePrerelease flag to upgrade to the latest stable or prelease package, whichever is latest.
Constraining Upgrades To Allowed Versions
By default, when running the
Update-Package command on a package (or updating the package using dialog),
it will be updated to the latest version in the feed. With the new support for updating all packages, there
may be cases in which you want to lock a package to a specific version range. For example, you may know in
advance that your application will only work with version 2.* of a package, but not 3.0 and above. In order
to prevent accidentally updating the package to 3, NuGet supports constraining the range of versions that
packages can be upgraded to by hand editing the
packages.config file using the
For example, the following example shows how to lock the
SomePackage package the version range 2.0 - 3.0
allowedVersions attribute accepts values using the version range format described
<?xml version="1.0" encoding="utf-8"?> <packages> <package id="SomePackage" version="2.1.0" allowedVersions="[2,3)" /> </packages>
Currently, locking a package to a specific version range requires hand-edited the packages.config file.
PM> Enable-PackageRestore Attempting to resolve dependency 'NuGet.CommandLine (≥ 1.4)'. Successfully installed 'NuGet.CommandLine 1.4.20615.182'. Successfully installed 'NuGet.Build 0.16'. Copying nuget.exe and msbuild scripts to D:\Code\StarterApps\Mvc3Application\.nuget Successfully uninstalled 'NuGet.Build 0.16'. Successfully uninstalled 'NuGet.CommandLine 1.4.20615.182'. Don't forget to commit the .nuget folder Updated 'Mvc3Application' to use 'NuGet.targets' Enabled package restore for Mvc3Application
And you’re done! So basically, the first command installs a NuGet package which brings in some helpful commands, and the second one runs one of those commands.
After doing this, you’ll notice a new .nuget folder under your solution, containing nuget.exe plus a couple msbuild target files. Make sure you commit that folder to source control! You’ll also find a few changes in your csproj files to trigger the restore functionality when you build.
Dependencies are no longer unnecessarily updated during package installation
Before NuGet 2.5, when a package was installed that depended on a package already installed in the project, the dependency would be updated as part of the new installation, even if the existing version satisfied the dependency.
Starting with NuGet 2.5, if a dependency version is already satisifed, the dependency will not be updated during other package installations.
The source repository contains package B with version 1.0.0 and 1.0.2. It also contains package A which has a dependency on B (>= 1.0.0).
Assume that the current project already has package B version 1.0.0 installed. Now you want to install package A.
In NuGet 2.2 and older:
- When installing package A, NuGet will auto-update B to 1.0.2, even though the existing version 1.0.0 already satisfies the dependency version constraint, which is >= 1.0.0.
In NuGet 2.5 and newer:
- NuGet will no longer update B, because it detects that the existing version 1.0.0 satisfies the dependency version constraint.