C＃从外部范围访问数据表

Question

I have JSON files with 2 objects... for this example "Country" and "Data". I'm trying to deserialize the "Data" object into datatable "sortedFileData" but have been unable to access the datatable from inside the while loop. I've found how to solve if creating a new class ( C#: access variable in the inner scope from the outer scope ) but I won't be doing that here.

        using (FileStream fs = new FileStream(selectedProject, FileMode.Open, FileAccess.Read))
        using (StreamReader sr = new StreamReader(fs))
        using (JsonTextReader reader = new JsonTextReader(sr))
        {
            DataTable sortedFileData = new DataTable();
            while (reader.Read())
            {
                if (reader.TokenType == JsonToken.StartObject)
                {
                    // Load each object from the stream and do something with it
                    JObject obj = JObject.Load(reader);
                    System.Windows.MessageBox.Show((string)obj["Country"]);
                    DataTable sortedFileData = JsonConvert.DeserializeObject<DataTable>((string)obj["Data"]);
                }
            }
        }

        string sorted = "Name ASC, Age ASC, Date ASC";
        DataView dtView = new DataView(sortedFileData) {Sort = sorted};

Sample JSON:

  { "Country": "England", "Data": [ { "Name": "Bill", "Age": "70", "Date": "2015-05-27" }, { "Name": "Sara", "Age": "36", "Date": "2015-01-21" }, { "Name": "Bob", "Age": "7", "Date": "2011-05-24" } ] } 

Answer 1

You can declare it outside of the loops and assign it in the same place.

    DataTable sortedFileData;

    using (FileStream fs = new FileStream(selectedProject, FileMode.Open, FileAccess.Read))
    using (StreamReader sr = new StreamReader(fs))
    using (JsonTextReader reader = new JsonTextReader(sr))
    {
        while (reader.Read())
        {
            if (reader.TokenType == JsonToken.StartObject)
            {
                // Load each object from the stream and do something with it
                JObject obj = JObject.Load(reader);
                System.Windows.MessageBox.Show((string)obj["Country"]);
                sortedFileData = JsonConvert.DeserializeObject<DataTable>((string)obj["DataTable1"]);
            }
        }
    }

    string sorted = "Name ASC, Age ASC, Date ASC";
    if (sortedFileData != null) 
    {
        DataView dtView = new DataView(sortedFileData) {Sort = sorted};
    }

And then you can just do a quick null check to make sure that everything went as expected.