Flurl example - post URL-encoded, receive JSON

flurl-example.cs

var result = await "http://localhost:8080/lzp/servRoot"
    .PostUrlEncodedAsync(new {
        className = "com.lzp.service.UserInfoService",
        methodName = "login",
        user_name = "123",
        user_pwd = "123"    
    })
    .ReceiveJson<TestResultModel>();

how send an array of elements example?
{
"requestTests": [
{
"idTest": {{idTest}}
}
]
}
??

{
"snIds": [
"HRNEW20210997",
"HRNEW202111002"
]
}

how send an array of elements