By default, Windows instances use WSUS (Windows Server Update Services) to obtain updates. This can lead to missing installation files for .NET Framework and language packs, causing errors such as source files not found or language packs not installable. This topic describes solutions for the installation failure of .NET Framework 3.5 or a language pack.
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This document is applicable to Windows Server 2012 R2 and later versions.
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For users of the Windows Server 2012 R2 system with the official image installed after June 2023, security patches may prevent the installation of .NET Framework 3.5. For this issue, see Failure to install .NET Framework 3.5 on Windows Server 2012 R2.
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To continue using the Windows Server 2012 R2 system, you can directly select the Windows Server 2012 R2 images with .NET Framework 3.5 pre-installed (win2012r2_9600_x64_dtc_zh-cn_40G_.Net3.5_alibase_20231204.vhd and win2012r2_9600_x64_dtc_en-us_40G_.Net3.5_alibase_20231204.vhd) from the community images in the ECS console to create an ECS instance. For guidance on locating these images, see Find images.
Problem description
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Problem 1: An error occurs during the installation of .NET Framework 3.5, as illustrated below.
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Problem 2: Language packs cannot be installed.
When attempting to switch languages in the Control Panel or searching for language options in Windows Update, language packs are not selectable or installable.
Cause
The default use of WSUS by Windows instances to obtain update sources can result in the absence of synchronized updates containing .NET Framework 3.5 or the corresponding language packs on the WSUS server. Consequently, the Windows instance cannot acquire these updates through WSUS, leading to missing installation files for .NET Framework and language packs, which in turn causes errors such as source files not found or language packs not installable.
Solutions
Solution 1: Install .NET Framework 3.5 using the Cloud Assistant plug-in
Log on to the ECS console.
In the left-side navigation pane, choose .
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At the top of the left-side navigation pane, select the resource group and region that contain the target resource.
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On the ECS Instances tab, click Execute Command in the Actions column of the row where the instance resides.
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Enter the following content in the command content, and select Execute Now. Due to the large file size, it is recommended to set the Timeout Period to more than 6000 seconds to ensure the download process completes smoothly. Keep other parameters as default, and then click Execute.
acs-plugin-manager.exe -e -P Windows_RestoreAndUpdate -p "-ByMedia iso -InstallFeature NetFx3"
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On the Command Execution Result tab, check the Execution Status of the command.
When it displays Execution Successful, it indicates that .NET Framework 3.5 has been successfully installed.
Solution 2: Install .NET Framework 3.5 by switching the update source
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Switch the update source to Windows Update.
Switch the update source using PowerShell
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Remotely connect to the Windows instance.
For detailed instructions, see Log on to a Windows instance by using the Workbench tool over the RDP protocol.
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Right-click the lower-left corner
, and then click Run. In the dialog box, enter
powershell
, and click OK. -
Enter
powershell
to open the PowerShell interface. -
In the PowerShell interface, execute the following command to modify the registry and set the update source to Windows Update.
Set-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU' -Name UseWUServer -Value 0 Restart-Service -Name wuauserv
Switch the update source by configuring group policy
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Remotely connect to the Windows instance.
For detailed instructions, see Log on to a Windows instance by using the Workbench tool over the RDP protocol.
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Right-click the lower-left corner
, and then click Run. In the dialog box, enter
gpedit.msc
, and click OK. -
Configure the group policy according to the system version.
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For Windows Server 2012 R2, Windows Server 2016, Windows Server 2019, or Windows Server 2022, follow these steps.
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In the Local Group Policy Editor, navigate to
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Double-click Specify Settings For Optional Component Installation And Component Repair, select Enabled, and then check Download Repair Content And Optional Features Directly From Windows Update Instead Of Windows Server Update Services (WSUS), and click OK.
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For Windows Server 2025, perform the following steps.
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In the Local Group Policy Editor, navigate to
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Double-click Specify Source Service For Specific Classes Of Windows Updates, select Enabled, set Feature Updates to Windows Update, and then click OK.
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Right-click the lower-left corner
, and then click Run. In the dialog box, enter
gpupdate /force
, and click OK to force the update of the local group policy.
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Install .NET Framework 3.5.
NoteThe memory usage of the Windows Server 2012 or Windows Server 2016 operating system is high. If you install other applications, memory usage may continue to increase, potentially causing insufficient memory and a failure to install .NET Framework. To prevent this, consider adding physical memory. If the instance is I/O optimized, it has a higher disk I/O capability and can complete data exchange faster than a regular instance when processing virtual memory read and write operations, thereby reducing the impact on system performance. For instructions on configuring virtual memory for Windows instances, see How to configure virtual memory for Windows instances.
Install using the Server Manager UI
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Click the lower-left corner
, and click Server Manager.
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In Server Manager, click Add Roles And Features.
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Proceed with the wizard using default configurations, and select .NET Framework 3.5 Features in the Features section.
Continue with the wizard to confirm the settings and complete the installation.
Install by executing PowerShell commands
Execute one of the following commands:
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Dism /Online /Enable-Feature /FeatureName:NetFX3 /All
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Install-WindowsFeature -Name NET-Framework-Features
ImportantIf the installation of .NET Framework reports errors such as
0x800F0906
or0x800F081F
, as shown below, refer to .NET Framework 3.5 installation errors for solutions. -
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(Conditionally required) If your Windows environment relies on WSUS for updates, execute the following commands to configure WSUS as the update source.
Set-ItemProperty -Path 'HKLM:\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU' -Name UseWUServer -Value 1 Restart-Service -Name wuauserv
References
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.NET Framework 3.5 is a software development framework provided by Microsoft, featuring core class libraries and runtime environments essential for developing and running applications based on the .NET Framework. The language packs for .NET Framework 3.5 are add-ons that enable support for multiple languages. For more information about .NET Framework, visit .NET Framework overview.
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For detailed steps on installing .NET Framework on other Windows Server versions, refer to the .NET Framework installation guide.
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To install .NET Framework 3.5/4.x on Windows Server 2016 or later, see Install .NET Framework on Windows Server 2016 or later.
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To install .NET Framework 3.5/4.x on Windows Server 2022, refer to Install .NET Framework on Windows Server 2022.
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