Type 'string[]' which is not a supported primitive type or a valid entity type. - How do I deserialize the json string?

Question

I have below json

 "PayloadData": {
      "CustomFields": ['test','test2'],
      "SampleNumber":"123"
     }

I am using below code to deserialize the json.

   Message message = JsonConvert.DeserializeObject<Message>(payloadData);

Here is my property in Message class

    /// <summary>
    /// Gets or sets CustomFields
    /// </summary>
    [Required]
    [DataMember(Name = "CustomFields")]
    public List<string> CustomFields{ get; set; }

But, I get below error.

"The property 'Message.CustomFields' could not be mapped, because it is of type 'string[]' which is not a supported primitive type or a valid entity type. Either explicitly map this property, or ignore it using the '[NotMapped]' attribute or by using 'EntityTypeBuilder.Ignore' in 'OnModelCreating'."

Solution

You can try using this online json to C# class generator to get the structure of a POCO required to deserialize a json string.

Then simply map it to your EF class (using AutoMapper for example):

So for this JSON:

 {
  "CustomFields": ['test','test2'],
  "SampleNumber":"123"
 }

this is the POCO that is generated:

public class RootObject
{
    public List<string> CustomFields { get; set; }
    public string SampleNumber { get; set; }
}

if this is your actual JSON:

    { "PayloadData":     
     {
      "CustomFields": ['test','test2'],
      "SampleNumber":"123"
     }
    }

this is how your POCO is supposed to look like:

public class PayloadData
{
    public List<string> CustomFields { get; set; }
    public string SampleNumber { get; set; }
}

public class RootObject
{
    public PayloadData PayloadData { get; set; }
}

Comments

[kudlatiger]

I am using entity framework and It's nothing to do with JSON serialization. Now, I am wondering how to store this list in database!

[JustLearning]

your payload data is a json string? Right? then you are trying to deserialize it into an EF code first class? If so, i am suggesting to first deserialize it to a POCO then map it to which ever EF class you require.

[Wylan Osorio]

@kudlatiger List or Array is not supported as a column type in the SQL database. You need make it as a separate class so it will be a separate table in the database. Let's say CustomField class with ID and Field properties, then update the Message class's CustomFields prop to be list of CustomField type.