https://stackoverflow.com/a/48083097/70345

Convert-ToDataTable.ps1

Function ConvertTo-DataTable {							# https://powersnippets.com/convertto-pson/
	[CmdletBinding()]Param(										# Version 01.00.01, by iRon
		[Parameter(Position=0, Mandatory=$true, ValueFromPipeline = $true)] [PSObject[]]$Object, [HashTable]$ColumnType = @{}
	)
	$TypeCast = @{
    Guid           = 'Guid', 'String'
    DateTime       = 'DateTime', 'String'
    DateTimeOffset = 'DateTimeOffset', 'String'
    Byte           = 'Byte', 'Char', 'Int16', 'Int32', 'Int64', 'UInt16', 'UInt32', 'UInt64', 'Decimal', 'Single', 'Double', 'String', 'Boolean'
    SByte          = 'SByte', 'Int16', 'Int32', 'Int64', 'Decimal', 'Single', 'Double', 'String', 'Boolean'
    Char           = 'Char', 'Int32', 'Int64', 'UInt16', 'UInt32', 'UInt64', 'String'
    TimeSpan       = 'TimeSpan', 'String'
    Int16          = 'Int16', 'Int32', 'Int64', 'Decimal', 'Single', 'Double', 'String', 'Boolean'
    Int32          = 'Int32', 'Int64', 'Decimal', 'Single', 'Double', 'String', 'TimeSpan', 'Boolean'
    Int64          = 'Int64', 'Decimal', 'Single', 'Double', 'String', 'TimeSpan', 'Boolean'
    UInt16         = 'Int32', 'Int64', 'UInt16', 'UInt32', 'UInt64', 'Decimal', 'Single', 'Double', 'Char', 'String', 'Boolean'
    UInt32         = 'Int64', 'UInt32', 'UInt64', 'Decimal', 'Single', 'Double', 'String', 'Boolean'
    UInt64         = 'UInt64', 'Decimal', 'Single', 'Double', 'String', 'Boolean'
    Decimal        = 'Decimal', 'Single', 'Double', 'String', 'Boolean'
    Single         = 'Single', 'Double', 'String', 'Boolean'
    Double         = 'Double', 'Single', 'String', 'Boolean'
    String         = 'String'
    Boolean        = 'Boolean', 'Byte', 'SByte', 'Int16', 'Int32', 'Int64', 'UInt16', 'UInt32', 'UInt64', 'Decimal', 'Single', 'Double', 'String'
	}
	$PipeLine = $Input | ForEach {$_}; If ($PipeLine) {$Object = $PipeLine}
	$DataTable = New-Object Data.DataTable
	$First = $Object | Select-Object -First 1
	$Properties = $First | Get-Member -Type Property; If (!$Properties) {$Properties = $First | Get-Member -Type NoteProperty}
	$Names = ForEach ($Property in $Properties) {$First.PSObject.Properties | Where {$_.Name -eq $Property.Name -and $_.IsGettable} | Select -Expand "Name"}
	ForEach($Name in $Names) {
    If ($ColumnType.ContainsKey($Name)) {$Type = $ColumnType.$Name}
    Else {
			$Types = $Object | Where-Object {$Null -ne $_.$Name} | ForEach {$_.$Name.GetType().Name} | Where-Object {$TypeCast.ContainsKey($_)} | Select-Object -Unique
			$Type = If ($Types -and ([bool] (Get-Member -InputObject $Types -MemberType Properties -Name "Count")) -and $Types.Count -gt 1) {
				$Cast = $TypeCast[$Types[0]]; ForEach ($Type in ($Types | Select-Object -Skip 1)) {$Cast = $Cast | Where-Object {$TypeCast[$Type] -Contains $_}}
                If ($Cast) {@($Cast)[0]}
                Else {'String'}
            }
            ElseIf ($Types) {$Types}
            Else {'String'}
		}
		$DataColumn = New-Object Data.DataColumn
		$DataColumn.ColumnName = $Name
		$DataColumn.DataType = [System.Type]::GetType("System.$Type")
		$DataTable.Columns.Add($DataColumn)
	}
	ForEach($RowObject in $Object) {
		$DataRow = $DataTable.NewRow()
		ForEach($Name in $Names) {$DataRow.Item($Name) = If ($Null -ne $RowObject.$Name) {$RowObject.$Name} Else {[DBNull]::Value}}
		$DataTable.Rows.Add($DataRow)
	}
	Write-Output (,($DataTable))
} Set-Alias ctdt ConvertTo-DataTable -Description "Converts a PowerShell object list to a DataTable"