SharePointDsc: SPFarmAdministrators: Resource fails with error message: An item with the same key has already been added

Error Message: PowerShell DSC resource MSFT_SPFarmAdministrators failed to execute Set-TargetResource functionality with error message: An item with the same key has already been added

Details of the scenario you tried and the problem that is occurring Just added one AD-group to Members in resource SPFarmAdministrators

Verbose logs showing the problem Suggested solution to the issue Case insensitive search of groups and accounts before adding them to Lists and Dictionaries

The DSC configuration that is used to reproduce the issue (as detailed as possible) PowerShell DSC:

SPFarmAdministrators 'FarmAdministrators' {
    PsDscRunAsCredential = $SetupCredential
    IsSingleInstance = 'Yes'
    Members = @($ConfigurationData.NonNodeData.SharePoint.AdministratorsGroup) +
                        @($ConfigurationData.NonNodeData.SharePoint.MonitorsGroup) | ? { $_ }
    DependsOn = @('[SPFarm]Farm')
}

MOF:

instance of MSFT_SPFarmAdministrators as $MSFT_SPFarmAdministrators1ref
{
    ResourceID = "[SPFarmAdministrators]FarmAdministrators";
    PsDscRunAsCredential = $MSFT_Credential29ref;
    Members = {
        "\SpIntAdmins"
    };
    SourceInfo = "C:\Users\JhonDoe\repos\Source\DSC\~Config\SPFarmDSC.ps1::785::13::SPFarmAdministrators";
    IsSingleInstance = "Yes";
    ModuleName = "SharePointDsc";
    ModuleVersion = "4.6.0";

    DependsOn = {

        "[SPFarm]Farm"
    };
    ConfigurationName = "SPFarmDSC";
};

The operating system the target node is running

OsName : Microsoft Windows Server 2016 Standard
OsOperatingSystemSKU : StandardServerEdition
OsArchitecture : 64-bit
WindowsBuildLabEx : 14393.3750.amd64fre.rs1_release.200601-1853
OsLanguage : en-US
OsMuiLanguages : {en-US}

Version of SharePoint that is used (e.g. SharePoint 2016) SharePoint 2016

Version and build of PowerShell the target node is running

PSVersion 5.1.14393.3471
PSEdition Desktop
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0...}
BuildVersion 10.0.14393.3471
CLRVersion 4.0.30319.42000
WSManStackVersion 3.0
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1

Version of the DSC module that was used ModuleVersion = “4.6.0”;