Background
In the below previous post
there were notes on how to enumerate & iterate over JSON documents. Let’s continue
down the rabbit hole. In this post we will look at how to use System.Text.Json namespace
to:
- Serialize to JSON
- Deserialize from JSON
Serialze to JSON
This means converting any type into a JSON string. We start off with a type named Computer and convert it into a JSON string. We call the JsonSerializer.Serialze() static method for this operation.
#!/usr/bin/env dotnet-script
using System;
using System.Text.Json;
class Computer
{
public string hostName { get; set; }
// In C# 6 and later, we can assign a default value to an auto property
public string domainName { get; set; } = "contoso.com";
public string IpAddress { get; set; }
}
var machine1 = new Computer()
{
hostName = "testvm01",
IpAddress = "10.10.10.101"
};
// serialize the object into JSON string
var json = JsonSerializer.Serialize(machine1);
Console.WriteLine(json);
Now doing the same in PowerShell 🤑
#!/usr/bin/env pwsh
using namespace System.Text.Json
class Computer {
[string] $hostName
[string] $domainName = "contoso.com" # this is the initial value
[string] $IpAddress
}
$machine1 = [Computer] @{
hostName = "testvm01"
IpAddress = "10.10.10.101"
}
# Invoke the static method on the class, it requires 2 arguments
# the Value to convert and any JsonSerializer options which we have passed as $null
$json = [JsonSerializer]::Serialize($machine1, $null)
Write-Host -Object $json
Deserialize from JSON
This means constructing a typed object from JSON string. No surprise there exists a JsonSerializer.Deserialze()
static method which can take a JSON string as input and can deserialized it into a typed object instance.
#!/usr/bin/env dotnet-script
using System;
using System.Text.Json;
using System.Net;
class Computer
{
public string hostName { get; set; }
public string domainName { get; set; } = "contoso.com";
public string IpAddress { get; set; }
}
string jsonComputer = "{\"domainName\":\"contoso.com\",\"hostName\":\"testvm01\",\"IpAddress\":\"10.10.10.101\"}";
var computerObject = JsonSerializer.Deserialize<Computer>(jsonComputer);
Console.WriteLine(computerObject.domainName);
In PowerShell the deserialization works really well with classes. If we have a type
defined in PowerShell class, we can use the Deserialze() static method and pass
it the type to deserialize the JSON string into.
#!/usr/bin/env pwsh
using namespace System.Text.Json
class Computer {
[string] $hostName
[string] $domainName = "contoso.com" # this is the initial value
[string] $IpAddress
}
$jsonComputer = '{"hostName":"testvm01","IpAddress":"10.10.10.101"}'
# Invoke the Deserialize static method on the class, it requires 3 arguments
# the Value to convert, and the type to convert it into and JsonSerializer options which we have passed as $null
$computer = [JsonSerializer]::Deserialize($jsonComputer, [Computer], $null)
# $computer | Get-Member # verify that the type got back is a Computer object type
Write-Host -Object $computer.domainName
Bonus
Above way to deserialize the JSON string into a typed object in PowerShell is pretty neat but we do mention another subtle way to achieve the same in our Book.
Cast-Initialization technique, which works by invoking an empty constrcutor and initializing values.
$jsonComputer = '{"hostName":"testvm01","IpAddress":"10.10.10.101"}'
[Computer]($jsonComputer | ConvertFrom-Json)
Conclusion 🗞
As a PowerShell developer, I learned using System.Text.Json namespace in PowerShell core to serialize/deserialize JSON in this post.
There will be a follow up post on this soon…