functions/Set/Set-ProjVersion.ps1

function Set-ProjVersion {
    param(
        [Parameter(Mandatory = $true)]
        [string]$ProjectDirectory,
        [Parameter(Mandatory = $true, ParameterSetName = 'FullVersion')]
        [Version]$FullVersion,
        [Parameter(Mandatory = $true, ParameterSetName = 'Revision')]
        [int]$Revision,
        [Parameter(Mandatory = $false)]
        [bool]$SetFileVersion = $true,
        [Parameter(Mandatory = $false)]
        [bool]$SetAssemblyVersion = $true
    )

    $projectFiles = Get-ChildItem $ProjectDirectory -Filter '*.csproj'
    foreach ($projectFile in $projectFiles) {
        $xml = New-Object System.Xml.XmlDocument
        $xml.Load($projectFile.FullName)

        # Check if project is .Net Core
        if ($null -ne $xml.Project.Attributes['Sdk']) {
            switch ($PsCmdlet.ParameterSetName) { 
                'FullVersion' { 
                    $newVersion = Convert-VersionToString $FullVersion
                    if ($SetAssemblyVersion) {
                        Write-Output "Setting AssemblyVersion $newVersion for $($projectFile.FullName)"
                        if ($null -eq $xml.Project.PropertyGroup.AssemblyVersion) {
                            $child = $xml.CreateElement("AssemblyVersion")
                            $xml.Project.PropertyGroup.AppendChild($child) | Out-Null
                        }

                        $xml.Project.PropertyGroup.AssemblyVersion = $newVersion
                    }
                    if ($SetFileVersion) {
                        Write-Output "Setting FileVersion $newVersion for $($projectFile.FullName)"
                        if ($null -eq $xml.Project.PropertyGroup.FileVersion) {
                            $child = $xml.CreateElement("FileVersion")
                            $xml.Project.PropertyGroup.AppendChild($child) | Out-Null
                        }

                        $xml.Project.PropertyGroup.FileVersion = $newVersion
                    }
                } 
                'Revision' { 
                    if ($SetAssemblyVersion) {
                        $asmVersion = [Version]$xml.Project.PropertyGroup.AssemblyVersion
                        $newVersion = Get-NewVersion $asmVersion $Revision

                        Write-Output "Setting AssemblyVersion $newVersion for $($projectFile.FullName)"
                        $xml.Project.PropertyGroup.AssemblyVersion = $newVersion
                    }
                    if ($SetFileVersion) {
                        $fileVersion = [Version]$xml.Project.PropertyGroup.FileVersion
                        $newVersion = Get-NewVersion $fileVersion $Revision

                        Write-Output "Setting FileVersion $newVersion for $($projectFile.FullName)"
                        $xml.Project.PropertyGroup.FileVersion = $newVersion
                    }
                } 
            } 
        }
        else {
            switch ($PsCmdlet.ParameterSetName) { 
                'FullVersion' { 
                    if ($SetAssemblyVersion) {
                        if ($xml.Project.PropertyGroup[0].ApplicationVersion) {
                            Write-Output "Setting AssemblyVersion $FullVersion for $($projectFile.FullName)"

                            $xml.Project.PropertyGroup[0].ApplicationVersion = (Convert-VersionToString $FullVersion)
                        }

                        Set-AssemblyInfoVersion -FilePath "$ProjectDirectory\Properties\AssemblyInfo.cs" -AttributeName 'AssemblyVersion' -FullVersion $FullVersion
                    }
                    if ($SetFileVersion) {
                        Set-AssemblyInfoVersion -FilePath "$ProjectDirectory\Properties\AssemblyInfo.cs" -AttributeName 'AssemblyFileVersion' -FullVersion $FullVersion
                    }
                } 
                'Revision' { 
                    if ($SetAssemblyVersion) {
                        $appVersion = [Version]$xml.Project.PropertyGroup[0].ApplicationVersion
                        if ($appVersion) {
                            $newVersion = Get-NewVersion $appVersion $Revision

                            Write-Output "Setting AssemblyVersion $newVersion for $($projectFile.FullName)"
                            $xml.Project.PropertyGroup[0].ApplicationVersion = $newVersion
                        }

                        $asmVersion = Get-AssemblyInfoVersion -FilePath "$ProjectDirectory\Properties\AssemblyInfo.cs" -AttributeName 'AssemblyVersion'
                        if ($asmVersion) {
                            Set-AssemblyInfoVersion -FilePath "$ProjectDirectory\Properties\AssemblyInfo.cs" -AttributeName 'AssemblyVersion' -FullVersion (Get-NewVersion $asmVersion $Revision) 
                        }
                    }

                    if ($SetFileVersion) {
                        $fileVersion = Get-AssemblyInfoVersion -FilePath "$ProjectDirectory\Properties\AssemblyInfo.cs" -AttributeName 'AssemblyFileVersion'
                        if ($fileVersion) {
                            Set-AssemblyInfoVersion -FilePath "$ProjectDirectory\Properties\AssemblyInfo.cs" -AttributeName 'AssemblyFileVersion' -FullVersion (Get-NewVersion $fileVersion $Revision)
                        }
                    }
                } 
            }
        }

        $xml.Save($projectFile.FullName)

        Write-Output "$($projectFile.FullName) successfully saved"
    }
}