This method doesn't require external libraries
using System.Web.Script.Serialization;
bool IsValidJson(string json)
{
try {
var serializer = new JavaScriptSerializer();
dynamic result = serializer.DeserializeObject(json);
return true;
} catch { return false; }
}
Alternate option using System.Text.Json
For .Net Core one can also use the System.Text.Json
namespace and parse using the JsonDocument
. Example is an extension method based on the namespace operations:
public static bool IsJsonValid(this string txt)
{
try { return JsonDocument.Parse(txt) != null; } catch {}
return false;
}
Use JContainer.Parse(str)
method to check if the str is a valid Json. If this throws exception then it is not a valid Json.
JObject.Parse
- Can be used to check if the string is a valid Json object
JArray.Parse
- Can be used to check if the string is a valid Json Array
JContainer.Parse
- Can be used to check for both Json object & Array
Here is a TryParse extension method based on Habib's answer:
public static bool TryParse(this string strInput, out JToken output)
{
if (String.IsNullOrWhiteSpace(strInput))
{
output = null;
return false;
}
strInput = strInput.Trim();
if ((strInput.StartsWith("{") && strInput.EndsWith("}")) || //For object
(strInput.StartsWith("[") && strInput.EndsWith("]"))) //For array
{
try
{
output = JToken.Parse(strInput);
return true;
}
catch (JsonReaderException jex)
{
//Exception in parsing json
//optional: LogError(jex);
output = null;
return false;
}
catch (Exception ex) //some other exception
{
//optional: LogError(ex);
output = null;
return false;
}
}
else
{
output = null;
return false;
}
}
Usage:
JToken jToken;
if (strJson.TryParse(out jToken))
{
// work with jToken
}
else
{
// not valid json
}
Regarding Tom Beech's answer; I came up with the following instead:
public bool ValidateJSON(string s)
{
try
{
JToken.Parse(s);
return true;
}
catch (JsonReaderException ex)
{
Trace.WriteLine(ex);
return false;
}
}
With a usage of the following:
if (ValidateJSON(strMsg))
{
var newGroup = DeserializeGroup(strMsg);
}
Just to add something to @Habib's answer, you can also check if given JSON is from a valid type:
public static bool IsValidJson<T>(this string strInput)
{
if(string.IsNullOrWhiteSpace(strInput)) return false;
strInput = strInput.Trim();
if ((strInput.StartsWith("{") && strInput.EndsWith("}")) || //For object
(strInput.StartsWith("[") && strInput.EndsWith("]"))) //For array
{
try
{
var obj = JsonConvert.DeserializeObject<T>(strInput);
return true;
}
catch // not valid
{
return false;
}
}
else
{
return false;
}
}
I'm using this one:
internal static bool IsValidJson(string data)
{
data = data.Trim();
try
{
if (data.StartsWith("{") && data.EndsWith("}"))
{
JToken.Parse(data);
}
else if (data.StartsWith("[") && data.EndsWith("]"))
{
JArray.Parse(data);
}
else
{
return false;
}
return true;
}
catch
{
return false;
}
}
I found that JToken.Parse incorrectly parses invalid JSON such as the following:
{
"Id" : ,
"Status" : 2
}
Paste the JSON string into http://jsonlint.com/ - it is invalid.
So I use:
public static bool IsValidJson(this string input)
{
input = input.Trim();
if ((input.StartsWith("{") && input.EndsWith("}")) || //For object
(input.StartsWith("[") && input.EndsWith("]"))) //For array
{
try
{
//parse the input into a JObject
var jObject = JObject.Parse(input);
foreach(var jo in jObject)
{
string name = jo.Key;
JToken value = jo.Value;
//if the element has a missing value, it will be Undefined - this is invalid
if (value.Type == JTokenType.Undefined)
{
return false;
}
}
}
catch (JsonReaderException jex)
{
//Exception in parsing json
Console.WriteLine(jex.Message);
return false;
}
catch (Exception ex) //some other exception
{
Console.WriteLine(ex.ToString());
return false;
}
}
else
{
return false;
}
return true;
}
JToken.Type
is available after a successful parse. This can be used to eliminate some of the preamble in the answers above and provide insight for finer control of the result. Entirely invalid input (e.g., "{----}".IsValidJson();
will still throw an exception).
public static bool IsValidJson(this string src)
{
try
{
var asToken = JToken.Parse(src);
return asToken.Type == JTokenType.Object || asToken.Type == JTokenType.Array;
}
catch (Exception) // Typically a JsonReaderException exception if you want to specify.
{
return false;
}
}
Json.Net reference for JToken.Type
: https://www.newtonsoft.com/json/help/html/T_Newtonsoft_Json_Linq_JTokenType.htm
Building on Habib's answer, you could write an extension method:
public static bool ValidateJSON(this string s)
{
try
{
JToken.Parse(s);
return true;
}
catch (JsonReaderException ex)
{
Trace.WriteLine(ex);
return false;
}
}
Which can then be used like this:
if(stringObject.ValidateJSON())
{
// Valid JSON!
}
Source: Stackoverflow.com