How to deserialize from JSON file with multiple objects

Question

So I have this JSON file. I want to get the data out of it in C#.

{
    "Server": [
        {
            "Name": "Server1",
            "AvgTemp": 36,
            "CurTemp": 50.3,
            "MaxTemp": 41,
            "MinTemp": 37
        },
        {
            "Name": "Server2",
            "AvgTemp": 36,
            "CurTemp": 50.3,
            "MaxTemp": 41,
            "MinTemp": 41
        },
        {
            "Name": "Server3",
            "AvgTemp": 36,
            "CurTemp": 50.3,
            "MaxTemp": 41,
            "MinTemp": 36
        },
        {
            "Name": "Server4",
            "AvgTemp": 36,
            "CurTemp": 50.3,
            "MaxTemp": 41,
            "MinTemp": 41.3
        }
    ]
}

I already tried this:

public ReadJson()
{
    //prevents the threads to block each other while accessing the json file
    using (var file = new FileStream("E:\\Programming\\Timmermann00\\Betrieblicher_Auftrag\\JSON\\Values.json", FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
    using (StreamReader r = new StreamReader(file))
    {
        string json = r.ReadToEnd();
        //Testing
        List<Values> values = JsonConvert.DeserializeObject<List<Values>>(json); 
                
    }
}

public class Values : INotifyPropertyChanged
{
    public Values()
    {
            
    }

    string Name { get; set; }

    string avgTemp; 
    public string AvgTemp { get => avgTemp; set
        {
            if(avgTemp!= value)
            {
                avgTemp = value;
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(AvgTemp)));
            }
        }
    }

    string maxTemp; 
    public string MaxTemp { get => maxTemp; set
        {
            if(maxTemp != value)
            {
                maxTemp = value;
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(MaxTemp)));
            }
        }
    }

    string minTemp; 
    public string MinTemp
    {
        get => minTemp; set
        {
            if (minTemp != value)
            {
                minTemp= value;
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(MinTemp)));
            }
        }
    }

    string curTemp;
    public string CurTemp
    {
        get => curTemp; set
        {
            if (curTemp != value)
            {
                curTemp = value;
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(CurTemp)));   
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

I get an error that says that my JSON file doesn't have any arrays in it so it can't convert into a List. Error message:

Cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[Betrieblicher_Auftrag.Values]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.

What is wrong?

Yong Shun · Accepted Answer · 2022-12-12 14:19:43Z

2

You need a Root class for the deserialization.

public class Root
{
    public List<Value> Server { get; set; }
}

And deserialize as Root instance.

Root root = JsonConvert.DeserializeObject<Root>(json);
List<Values> values = root.Server;

answered Dec 12, 2022 at 14:19

Yong Shun

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2 Comments

Tim Harbeck Over a year ago

Thank you for the fast help. It worked. Can you explain me what the exact diffrence is between you "Root" class an my way to convert it directly into an list?

Yong Shun Over a year ago

Because your JSON is an object which contains property that holds the array with List<Values> type. You should deserialize the JSON as Root object first and next retrieve the array.

Red-Dot · Accepted Answer · 2022-12-12 14:25:54Z

Working code.

can you try with this.

public ReadJson()
    {
        //prevents the threads to block each other while accessing the json file
        using (var file = new FileStream("E:\\Programming\\Timmermann00\\Betrieblicher_Auftrag\\JSON\\Values.json", FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
        using (StreamReader r = new StreamReader(file))
        {
            string json = r.ReadToEnd();
            //Testing
         var servers = JsonConvert.DeserializeObject<Server>(json);
            List<Values> values = server.Server;
            
        }
    }
}

public List<Values> Server {get; set;}
public class Values:INotifyPropertyChanged
{
    public Values()
    {
        
    }
    
    string Name { get; set; }

    string avgTemp; 
    public string AvgTemp { get => avgTemp; set
        {
            if(avgTemp!= value)
            {
                avgTemp = value;
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(AvgTemp)));
            }
        }
    }
    string maxTemp; 
    public string MaxTemp { get => maxTemp; set
        {
            if(maxTemp != value)
            {
                maxTemp = value;
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(MaxTemp)));
            }
        }
    }

    string minTemp; 
    public string MinTemp
    {
        get => minTemp; set
        {
            if (minTemp != value)
            {
                minTemp= value;
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(MinTemp)));
            }
        }
    }

    string curTemp;
    public string CurTemp
    {
        get => curTemp; set
        {
            if (curTemp != value)
            {
                curTemp = value;
                this.PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(CurTemp)));   
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
}

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