Troubleshooting problem: Unable to resolve JSON deserialization issue in .NET service

I've been struggling with this problem for a couple of days now without any success. My goal is to deserialize a JSON object in VB.NET, but I keep encountering the following error:

"Type 'System.String' is not supported for deserialization of an array."

Despite trying all the solutions I could find, none seem to work.

Below is my JQuery code:

          $.ajax({
                type: "POST",
                url: "/Services/Data_Services.asmx/AssignRoles",
                contentType: "application/json; charset=utf-8",
                data: JSON.stringify({ roleAssignments: roleassignments }),
                datatype: "json",
                success: function (data) {
                    alert("Group assignments successfully set");
                },
                error: function (response) {
                    alert(response.responseText);
                },
                failure: function (response) {
                    alert(response.responseText);
                }
            });

This is the output: {"roleAssignments":[{"groupid":"2","role":"4","staffid":"111"},{"groupid":"2","role":"5","staffid":"999"},{"groupid":"2","role":"6","staffid":"999"},{"groupid":"2","role":"7","staffid":"0"},{"groupid":"2","role":"8","staffid":"999"},{"groupid":"2","role":"9","staffid":"15"}]}

(I have validated the JSON using JSONLint)

Here is the .NET code that throws an error during deserialization:

Public Function AssignRoles(ByVal roleAssignments As String) As String()
[.........] 

Dim aRoleList As New List(Of roleAssignments)
Dim js As New System.Web.Script.Serialization.JavaScriptSerializer
aRoleList = js.Deserialize(Of List(Of roleAssignments))(roleAssignments)

[.........]
End Function

Public Class roleAssignments
   Public Property groupid As String
   Public Property role As String
   Public Property staffid As String
End Class

Any suggestions on how to resolve this issue would be greatly appreciated. I have tried various approaches and consulted other examples, but I can't seem to figure out what's causing the problem.

Thank you.

Answer №1

After working through the problem, I was able to find a solution without assistance. It turned out that the List object wasn't causing the issue, but rather the way I was passing JSON into the web service. To resolve it, I made sure to escape the quotes and adjusted the syntax used in JSON.stringify. When nesting JSON.stringify within another JSON.stringify, it automatically adds escapes to the quotes.

$.ajax({
                type: "POST",
                url: "/Services/Data_Services.asmx/AssignRoles",
                data: "{ \"roleJSON\": " + JSON.stringify(JSON.stringify(roleassignments)) + "}",
                dataType: "json",
                contentType: "application/json; charset=utf-8",
                success: function (data) {
                        // parse return data here....
                        showSuccessMessage("Group assignments set");
                },
                error: function (response) {
                    alert("Error occurred:" + response.responseText);
                },
                failure: function (response) {
                    alert("Insert failed: " + response.responseText);
                }
            });

In handling the VB code, I made minimal changes which included removing the new keyword from the List declaration and updating the name of the JSON string being passed in.

 Dim aRoleList As List(Of roleAssignments)
 Dim returnedValue As New List(Of String)
 Try
     Dim js As New System.Web.Script.Serialization.JavaScriptSerializer
     aRoleList = js.Deserialize(Of List(Of roleAssignments))(roleJSON)
[.....]

Sharing this resolution serves as a reference point for others encountering similar challenges. In software development, it often comes down to pinpointing and correcting syntax issues.

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