Cannot deserialize the current JSON object (e.g. {"name":"value"})

By: Suresh Dasari Feb 9, 2017

Introduction:

Here we will learn how to solve the problem of cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[userdetails]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly. Generally we will get this error whenever our deserialized JSON object returning list of object items but we are trying to hold only single item.

Description:

In previous articles I explained asp.net json serialization and deserialization in c#, vb.net, asp.net set custom error page inn web.config, unrecognized escape sequence in file path in c#, vb.net, cannot convert string to type double is not valid in vb.net, jQuery show error message in ajax call response with example, convert json string to json object with example and many more articles related to in JSON, asp.net, mvc, c#, vb.net. Now I will explain how to solve the problem cannot deserialize the current JSON object (e.g. {"name":"value"}) into type 'System.Collections.Generic.List`1[userdetails]' because the type requires a JSON array (e.g. [1,2,3]) to deserialize correctly.

We are getting following error in our application whenever we are try to deserialize the JSON string in asp.net by using newtonsoft json.

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

Actually this problem occurred whenever our JSON deserialization method returns more than one list item but we are trying to hold it as single item like as shown following.

C# Code

string strmsg = "[{\"userid\":1,\"username\":\"suresh\",\"location\":\"chennai\"},{\"userid\":2,\"username\":\"rohini\",\"location\":\"guntur\"}]";

userdetails user = JsonConvert.DeserializeObject<userdetails>(strmsg);

VB.NET Code

Dim strmsg As String = "[{""userid"":1,""username"":""suresh"",""location"":""chennai""},{""userid"":2,""username"":""rohini"",""location"":""guntur""}]"

Dim user As userdetails = JsonConvert.DeserializeObject(Of userdetails)(strmsg)

We need to change userdetails user parameter to var user like as shown following because our deserialization method returning more than one list item.

C# Code

string strmsg = "[{\"userid\":1,\"username\":\"suresh\",\"location\":\"chennai\"},{\"userid\":2,\"username\":\"rohini\",\"location\":\"guntur\"}]";

var user = JsonConvert.DeserializeObject<List<userdetails>>(strmsg);

VB.NET Code

Dim strmsg As String = "[{""userid"":1,""username"":""suresh"",""location"":""chennai""},{""userid"":2,""username"":""rohini"",""location"":""guntur""}]"

Dim user = JsonConvert.DeserializeObject(Of List(Of userdetails))(strmsg)

If you want complete example to implement serialization and deserialization for JSON data create new web application and open your Default.aspx page and write the code like as shown below.

<title>JSON Serialization and Deserialization in Asp.Net</title>

</head>

<body>

<asp:Button ID="btnSerialize" runat="server" Text="Serialize" OnClick="btnSerialize_Click" />

<asp:Button ID="btnDeserialize" runat="server" Text="DeSerialize" OnClick="btnDeserialize_Click" />

<div>

Serialized Data: <asp:Label ID="lblserial" runat="server"/>

</div>

<div>

DeSerialized Data: <asp:Label ID="lbldeserial" runat="server"/>

</div>

</form>

</body>

</html>

Now open code behind file and write the code like as shown below

C# Code

using System;

using System.Collections.Generic;

using Newtonsoft.Json;

public partial class _Default : System.Web.UI.Page

{

protected void Page_Load(object sender, EventArgs e)

{

}

protected void btnSerialize_Click(object sender, EventArgs e)

{

List<userdetails> details = new List<userdetails>();

userdetails user = new userdetails();

details.Add(new userdetails { userid = 1, username = "suresh", location = "chennai" });

details.Add(new userdetails { userid = 2, username = "rohini", location = "guntur" });

details.Add(new userdetails { userid = 3, username = "praveen", location = "bangalore" });

details.Add(new userdetails { userid = 4, username = "sateesh", location = "vizag" });

details.Add(new userdetails { userid = 5, username = "madhav", location = "nagpur" });

details.Add(new userdetails { userid = 6, username = "honey", location = "nagpur" });

string strserialize = JsonConvert.SerializeObject(details);

lblserial.Text = strserialize;

}

protected void btnDeserialize_Click(object sender, EventArgs e)

{

string strmsg = "[{\"userid\":1,\"username\":\"suresh\",\"location\":\"chennai\"},{\"userid\":2,\"username\":\"rohini\",\"location\":\"guntur\"}]";

var user = JsonConvert.DeserializeObject<List<userdetails>>(strmsg);

}

class userdetails

{

public int userid { get; set; }

public string username { get; set; }

public string location { get; set; }

}

VB.NET Code

Imports Newtonsoft.Json

Partial Class VBCode

Inherits System.Web.UI.Page

Protected Sub Page_Load(sender As Object, e As EventArgs) Handles Me.Load

End Sub

Protected Sub btnSerialize_Click(sender As Object, e As EventArgs)

Dim details As New List(Of userdetails)()

Dim user As New userdetails()