Parsing JSON using Json.net
C#ParsingSerializationjson.netC# Problem Overview
I'm trying to parse some JSON using the JSon.Net library. The documentation seems a little sparse and I'm confused as to how to accomplish what I need. Here is the format for the JSON I need to parse through.
{
"displayFieldName" : "OBJECT_NAME",
"fieldAliases" : {
"OBJECT_NAME" : "OBJECT_NAME",
"OBJECT_TYPE" : "OBJECT_TYPE"
},
"positionType" : "point",
"reference" : {
"id" : 1111
},
"objects" : [ {
"attributes" : {
"OBJECT_NAME" : "test name",
"OBJECT_TYPE" : "test type"
},
"position" : {
"x" : 5,
"y" : 7
}
} ]
}
The only data I really need from this is the stuff in the objects array. Is it possible for me to parse through that with something like the JSonTextReader and just pull out the things I want, like OBJECT_TYPE and the x and y position? I can't seem to get JSonTextReader to work the way I want it to and I find little to no examples of usage for it.
It seems like serializing first then using LINQ with my object would be ideal and every example I find discusses serializing the JSON first, but I'm not sure how I would build an object for this structure. Particularly the objects array which would need to be something like a list of Pairs of attribute and position objects. I have no idea how I would code my object so JSon.Net would know how to serialize that.
I thought I could write my own simple parser to just pull out everything I need into an attributes object that I created, but I'm having little luck.
Hopefully this all makes sense, any ideas?
C# Solutions
Solution 1 - C#
I don't know about JSON.NET, but it works fine with JavaScriptSerializer from System.Web.Extensions.dll (.NET 3.5 SP1):
using System.Collections.Generic;
using System.Web.Script.Serialization;
public class NameTypePair
{
public string OBJECT_NAME { get; set; }
public string OBJECT_TYPE { get; set; }
}
public enum PositionType { none, point }
public class Ref
{
public int id { get; set; }
}
public class SubObject
{
public NameTypePair attributes { get; set; }
public Position position { get; set; }
}
public class Position
{
public int x { get; set; }
public int y { get; set; }
}
public class Foo
{
public Foo() { objects = new List<SubObject>(); }
public string displayFieldName { get; set; }
public NameTypePair fieldAliases { get; set; }
public PositionType positionType { get; set; }
public Ref reference { get; set; }
public List<SubObject> objects { get; set; }
}
static class Program
{
const string json = @"{
""displayFieldName"" : ""OBJECT_NAME"",
""fieldAliases"" : {
""OBJECT_NAME"" : ""OBJECT_NAME"",
""OBJECT_TYPE"" : ""OBJECT_TYPE""
},
""positionType"" : ""point"",
""reference"" : {
""id"" : 1111
},
""objects"" : [
{
""attributes"" : {
""OBJECT_NAME"" : ""test name"",
""OBJECT_TYPE"" : ""test type""
},
""position"" :
{
""x"" : 5,
""y"" : 7
}
}
]
}";
static void Main()
{
JavaScriptSerializer ser = new JavaScriptSerializer();
Foo foo = ser.Deserialize<Foo>(json);
}
}
Edit:
Json.NET works using the same JSON and classes.
Foo foo = JsonConvert.DeserializeObject<Foo>(json);
Solution 2 - C#
Edit: Thanks Marc, read up on the struct vs class issue and you're right, thank you!
I tend to use the following method for doing what you describe, using a static method of JSon.Net:
MyObject deserializedObject = JsonConvert.DeserializeObject<MyObject>(json);
Link: Serializing and Deserializing JSON with Json.NET
For the Objects list, may I suggest using generic lists out made out of your own small class containing attributes and position class. You can use the Point struct in System.Drawing (System.Drawing.Point or System.Drawing.PointF for floating point numbers) for you X and Y.
After object creation it's much easier to get the data you're after vs. the text parsing you're otherwise looking at.
Solution 3 - C#
(This question came up high on a search engine result, but I ended up using a different approach. Adding an answer to this old question in case other people with similar questions read this)
You can solve this with Json.Net and make an extension method to handle the items you want to loop:
public static Tuple<string, int, int> ToTuple(this JToken token)
{
var type = token["attributes"]["OBJECT_TYPE"].ToString();
var x = token["position"]["x"].Value<int>();
var y = token["position"]["y"].Value<int>();
return new Tuple<string, int, int>(type, x, y);
}
And then access the data like this: (scenario: writing to console):
var tuples = JObject.Parse(myJsonString)["objects"].Select(item => item.ToTuple()).ToList();
tuples.ForEach(t => Console.WriteLine("{0}: ({1},{2})", t.Item1, t.Item2, t.Item3));
Solution 4 - C#
/*
* This method takes in JSON in the form returned by javascript's
* JSON.stringify(Object) and returns a string->string dictionary.
* This method may be of use when the format of the json is unknown.
* You can modify the delimiters, etc pretty easily in the source
* (sorry I didn't abstract it--I have a very specific use).
*/
public static Dictionary<string, string> jsonParse(string rawjson)
{
Dictionary<string, string> outdict = new Dictionary<string, string>();
StringBuilder keybufferbuilder = new StringBuilder();
StringBuilder valuebufferbuilder = new StringBuilder();
StringReader bufferreader = new StringReader(rawjson);
int s = 0;
bool reading = false;
bool inside_string = false;
bool reading_value = false;
//break at end (returns -1)
while (s >= 0)
{
s = bufferreader.Read();
//opening of json
if (!reading)
{
if ((char)s == '{' && !inside_string && !reading) reading = true;
continue;
}
else
{
//if we find a quote and we are not yet inside a string, advance and get inside
if (!inside_string)
{
//read past the quote
if ((char)s == '\"') inside_string = true;
continue;
}
if (inside_string)
{
//if we reached the end of the string
if ((char)s == '\"')
{
inside_string = false;
s = bufferreader.Read(); //advance pointer
if ((char)s == ':')
{
reading_value = true;
continue;
}
if (reading_value && (char)s == ',')
{
//we know we just ended the line, so put itin our dictionary
if (!outdict.ContainsKey(keybufferbuilder.ToString())) outdict.Add(keybufferbuilder.ToString(), valuebufferbuilder.ToString());
//and clear the buffers
keybufferbuilder.Clear();
valuebufferbuilder.Clear();
reading_value = false;
}
if (reading_value && (char)s == '}')
{
//we know we just ended the line, so put itin our dictionary
if (!outdict.ContainsKey(keybufferbuilder.ToString())) outdict.Add(keybufferbuilder.ToString(), valuebufferbuilder.ToString());
//and clear the buffers
keybufferbuilder.Clear();
valuebufferbuilder.Clear();
reading_value = false;
reading = false;
break;
}
}
else
{
if (reading_value)
{
valuebufferbuilder.Append((char)s);
continue;
}
else
{
keybufferbuilder.Append((char)s);
continue;
}
}
}
else
{
switch ((char)s)
{
case ':':
reading_value = true;
break;
default:
if (reading_value)
{
valuebufferbuilder.Append((char)s);
}
else
{
keybufferbuilder.Append((char)s);
}
break;
}
}
}
}
return outdict;
}
Solution 5 - C#
You use the JSON class and then call the GetData() function.
/// <summary>
/// This class encodes and decodes JSON strings.
/// Spec. details, see http://www.json.org/
///
/// JSON uses Arrays and Objects. These correspond here to the datatypes ArrayList and Hashtable.
/// All numbers are parsed to doubles.
/// </summary>
using System;
using System.Collections;
using System.Globalization;
using System.Text;
public class JSON
{
public const int TOKEN_NONE = 0;
public const int TOKEN_CURLY_OPEN = 1;
public const int TOKEN_CURLY_CLOSE = 2;
public const int TOKEN_SQUARED_OPEN = 3;
public const int TOKEN_SQUARED_CLOSE = 4;
public const int TOKEN_COLON = 5;
public const int TOKEN_COMMA = 6;
public const int TOKEN_STRING = 7;
public const int TOKEN_NUMBER = 8;
public const int TOKEN_TRUE = 9;
public const int TOKEN_FALSE = 10;
public const int TOKEN_NULL = 11;
private const int BUILDER_CAPACITY = 2000;
/// <summary>
/// Parses the string json into a value
/// </summary>
/// <param name="json">A JSON string.</param>
/// <returns>An ArrayList, a Hashtable, a double, a string, null, true, or false</returns>
public static object JsonDecode(string json)
{
bool success = true;
return JsonDecode(json, ref success);
}
/// <summary>
/// Parses the string json into a value; and fills 'success' with the successfullness of the parse.
/// </summary>
/// <param name="json">A JSON string.</param>
/// <param name="success">Successful parse?</param>
/// <returns>An ArrayList, a Hashtable, a double, a string, null, true, or false</returns>
public static object JsonDecode(string json, ref bool success)
{
success = true;
if (json != null) {
char[] charArray = json.ToCharArray();
int index = 0;
object value = ParseValue(charArray, ref index, ref success);
return value;
} else {
return null;
}
}
/// <summary>
/// Converts a Hashtable / ArrayList object into a JSON string
/// </summary>
/// <param name="json">A Hashtable / ArrayList</param>
/// <returns>A JSON encoded string, or null if object 'json' is not serializable</returns>
public static string JsonEncode(object json)
{
StringBuilder builder = new StringBuilder(BUILDER_CAPACITY);
bool success = SerializeValue(json, builder);
return (success ? builder.ToString() : null);
}
protected static Hashtable ParseObject(char[] json, ref int index, ref bool success)
{
Hashtable table = new Hashtable();
int token;
// {
NextToken(json, ref index);
bool done = false;
while (!done) {
token = LookAhead(json, index);
if (token == JSON.TOKEN_NONE) {
success = false;
return null;
} else if (token == JSON.TOKEN_COMMA) {
NextToken(json, ref index);
} else if (token == JSON.TOKEN_CURLY_CLOSE) {
NextToken(json, ref index);
return table;
} else {
// name
string name = ParseString(json, ref index, ref success);
if (!success) {
success = false;
return null;
}
// :
token = NextToken(json, ref index);
if (token != JSON.TOKEN_COLON) {
success = false;
return null;
}
// value
object value = ParseValue(json, ref index, ref success);
if (!success) {
success = false;
return null;
}
table[name] = value;
}
}
return table;
}
protected static ArrayList ParseArray(char[] json, ref int index, ref bool success)
{
ArrayList array = new ArrayList();
// [
NextToken(json, ref index);
bool done = false;
while (!done) {
int token = LookAhead(json, index);
if (token == JSON.TOKEN_NONE) {
success = false;
return null;
} else if (token == JSON.TOKEN_COMMA) {
NextToken(json, ref index);
} else if (token == JSON.TOKEN_SQUARED_CLOSE) {
NextToken(json, ref index);
break;
} else {
object value = ParseValue(json, ref index, ref success);
if (!success) {
return null;
}
array.Add(value);
}
}
return array;
}
protected static object ParseValue(char[] json, ref int index, ref bool success)
{
switch (LookAhead(json, index)) {
case JSON.TOKEN_STRING:
return ParseString(json, ref index, ref success);
case JSON.TOKEN_NUMBER:
return ParseNumber(json, ref index, ref success);
case JSON.TOKEN_CURLY_OPEN:
return ParseObject(json, ref index, ref success);
case JSON.TOKEN_SQUARED_OPEN:
return ParseArray(json, ref index, ref success);
case JSON.TOKEN_TRUE:
NextToken(json, ref index);
return true;
case JSON.TOKEN_FALSE:
NextToken(json, ref index);
return false;
case JSON.TOKEN_NULL:
NextToken(json, ref index);
return null;
case JSON.TOKEN_NONE:
break;
}
success = false;
return null;
}
protected static string ParseString(char[] json, ref int index, ref bool success)
{
StringBuilder s = new StringBuilder(BUILDER_CAPACITY);
char c;
EatWhitespace(json, ref index);
// "
c = json[index++];
bool complete = false;
while (!complete) {
if (index == json.Length) {
break;
}
c = json[index++];
if (c == '"') {
complete = true;
break;
} else if (c == '\\') {
if (index == json.Length) {
break;
}
c = json[index++];
if (c == '"') {
s.Append('"');
} else if (c == '\\') {
s.Append('\\');
} else if (c == '/') {
s.Append('/');
} else if (c == 'b') {
s.Append('\b');
} else if (c == 'f') {
s.Append('\f');
} else if (c == 'n') {
s.Append('\n');
} else if (c == 'r') {
s.Append('\r');
} else if (c == 't') {
s.Append('\t');
} else if (c == 'u') {
int remainingLength = json.Length - index;
if (remainingLength >= 4) {
// parse the 32 bit hex into an integer codepoint
uint codePoint;
if (!(success = UInt32.TryParse(new string(json, index, 4), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out codePoint))) {
return "";
}
// convert the integer codepoint to a unicode char and add to string
s.Append(Char.ConvertFromUtf32((int)codePoint));
// skip 4 chars
index += 4;
} else {
break;
}
}
} else {
s.Append(c);
}
}
if (!complete) {
success = false;
return null;
}
return s.ToString();
}
protected static double ParseNumber(char[] json, ref int index, ref bool success)
{
EatWhitespace(json, ref index);
int lastIndex = GetLastIndexOfNumber(json, index);
int charLength = (lastIndex - index) + 1;
double number;
success = Double.TryParse(new string(json, index, charLength), NumberStyles.Any, CultureInfo.InvariantCulture, out number);
index = lastIndex + 1;
return number;
}
protected static int GetLastIndexOfNumber(char[] json, int index)
{
int lastIndex;
for (lastIndex = index; lastIndex < json.Length; lastIndex++) {
if ("0123456789+-.eE".IndexOf(json[lastIndex]) == -1) {
break;
}
}
return lastIndex - 1;
}
protected static void EatWhitespace(char[] json, ref int index)
{
for (; index < json.Length; index++) {
if (" \t\n\r".IndexOf(json[index]) == -1) {
break;
}
}
}
protected static int LookAhead(char[] json, int index)
{
int saveIndex = index;
return NextToken(json, ref saveIndex);
}
protected static int NextToken(char[] json, ref int index)
{
EatWhitespace(json, ref index);
if (index == json.Length) {
return JSON.TOKEN_NONE;
}
char c = json[index];
index++;
switch (c) {
case '{':
return JSON.TOKEN_CURLY_OPEN;
case '}':
return JSON.TOKEN_CURLY_CLOSE;
case '[':
return JSON.TOKEN_SQUARED_OPEN;
case ']':
return JSON.TOKEN_SQUARED_CLOSE;
case ',':
return JSON.TOKEN_COMMA;
case '"':
return JSON.TOKEN_STRING;
case '0': case '1': case '2': case '3': case '4':
case '5': case '6': case '7': case '8': case '9':
case '-':
return JSON.TOKEN_NUMBER;
case ':':
return JSON.TOKEN_COLON;
}
index--;
int remainingLength = json.Length - index;
// false
if (remainingLength >= 5) {
if (json[index] == 'f' &&
json[index + 1] == 'a' &&
json[index + 2] == 'l' &&
json[index + 3] == 's' &&
json[index + 4] == 'e') {
index += 5;
return JSON.TOKEN_FALSE;
}
}
// true
if (remainingLength >= 4) {
if (json[index] == 't' &&
json[index + 1] == 'r' &&
json[index + 2] == 'u' &&
json[index + 3] == 'e') {
index += 4;
return JSON.TOKEN_TRUE;
}
}
// null
if (remainingLength >= 4) {
if (json[index] == 'n' &&
json[index + 1] == 'u' &&
json[index + 2] == 'l' &&
json[index + 3] == 'l') {
index += 4;
return JSON.TOKEN_NULL;
}
}
return JSON.TOKEN_NONE;
}
protected static bool SerializeValue(object value, StringBuilder builder)
{
bool success = true;
if (value is string) {
success = SerializeString((string)value, builder);
} else if (value is Hashtable) {
success = SerializeObject((Hashtable)value, builder);
} else if (value is ArrayList) {
success = SerializeArray((ArrayList)value, builder);
} else if ((value is Boolean) && ((Boolean)value == true)) {
builder.Append("true");
} else if ((value is Boolean) && ((Boolean)value == false)) {
builder.Append("false");
} else if (value is ValueType) {
// thanks to ritchie for pointing out ValueType to me
success = SerializeNumber(Convert.ToDouble(value), builder);
} else if (value == null) {
builder.Append("null");
} else {
success = false;
}
return success;
}
protected static bool SerializeObject(Hashtable anObject, StringBuilder builder)
{
builder.Append("{");
IDictionaryEnumerator e = anObject.GetEnumerator();
bool first = true;
while (e.MoveNext()) {
string key = e.Key.ToString();
object value = e.Value;
if (!first) {
builder.Append(", ");
}
SerializeString(key, builder);
builder.Append(":");
if (!SerializeValue(value, builder)) {
return false;
}
first = false;
}
builder.Append("}");
return true;
}
protected static bool SerializeArray(ArrayList anArray, StringBuilder builder)
{
builder.Append("[");
bool first = true;
for (int i = 0; i < anArray.Count; i++) {
object value = anArray[i];
if (!first) {
builder.Append(", ");
}
if (!SerializeValue(value, builder)) {
return false;
}
first = false;
}
builder.Append("]");
return true;
}
protected static bool SerializeString(string aString, StringBuilder builder)
{
builder.Append("\"");
char[] charArray = aString.ToCharArray();
for (int i = 0; i < charArray.Length; i++) {
char c = charArray[i];
if (c == '"') {
builder.Append("\\\"");
} else if (c == '\\') {
builder.Append("\\\\");
} else if (c == '\b') {
builder.Append("\\b");
} else if (c == '\f') {
builder.Append("\\f");
} else if (c == '\n') {
builder.Append("\\n");
} else if (c == '\r') {
builder.Append("\\r");
} else if (c == '\t') {
builder.Append("\\t");
} else {
int codepoint = Convert.ToInt32(c);
if ((codepoint >= 32) && (codepoint <= 126)) {
builder.Append(c);
} else {
builder.Append("\\u" + Convert.ToString(codepoint, 16).PadLeft(4, '0'));
}
}
}
builder.Append("\"");
return true;
}
protected static bool SerializeNumber(double number, StringBuilder builder)
{
builder.Append(Convert.ToString(number, CultureInfo.InvariantCulture));
return true;
}
}
//parse and show entire json in key-value pair
Hashtable HTList = (Hashtable)JSON.JsonDecode("completejsonstring");
public void GetData(Hashtable HT)
{
IDictionaryEnumerator ienum = HT.GetEnumerator();
while (ienum.MoveNext())
{
if (ienum.Value is ArrayList)
{
ArrayList arnew = (ArrayList)ienum.Value;
foreach (object obj in arnew)
{
Hashtable hstemp = (Hashtable)obj;
GetData(hstemp);
}
}
else
{
Console.WriteLine(ienum.Key + "=" + ienum.Value);
}
}
}