elsa-workflows/elsa-core · error · JsonException

Expected an array of strings.

Error message

Expected an array of strings.

What it means

CaseInsensitiveHashSetConverter.Read deserializes a HashSet<string> of secret tags. If the JSON token is neither null nor a start-array, the converter throws this JsonException because only a JSON array is a valid representation for tags. This indicates malformed or incompatible stored/serialized JSON for the Tags property.

Solutions

1. Fix the JSON so tags is an array of strings, e.g. "tags": ["prod", "api"].
2. If the value should be empty, set it to null (converter returns an empty set) or an empty array [].
3. Migrate old-format documents to the current Secret JSON schema.
4. Validate external JSON against the Secret schema before deserializing.

Example fix

// before
{ "tags": "prod,api" }

// after
{ "tags": ["prod", "api"] }

using var doc = JsonDocument.Parse(json);
if (doc.RootElement.TryGetProperty("tags", out var t) && t.ValueKind is not (JsonValueKind.Array or JsonValueKind.Null))
    throw new JsonException("'tags' must be an array of strings.");

static bool IsValidTagsJson(JsonElement el) => el.ValueKind is JsonValueKind.Array or JsonValueKind.Null;

try { return JsonSerializer.Deserialize<Secret>(json, options); }
catch (JsonException ex) when (ex.Message.Contains("array of strings")) { /* repair tags field or reject payload */ }

When it happens

Trigger: Deserializing a Secret (or payload containing Tags) where the tags field is a string, object, or number instead of a JSON array — e.g. stored data from an older schema or hand-edited JSON.

Common situations: Manual database edits of secret documents; data produced by a different serializer or library version; feeding user-supplied JSON into a Secret-shaped model without validation.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Expected a string tag.
• Expected an object of string metadata values.
• Cannot deserialize to .
• Failed to deserialize
• The binding to activity type

AI-assisted analysis of elsa-workflows/elsa-core@fe9217bdfa (2026-09-13). Data as JSON: /api/errors/8a7cf0332e11c258. Report an issue: GitHub.

Appendix: source

Thrown at src/modules/Elsa.Secrets/Models/CaseInsensitiveHashSetConverter.cs:14

using System.Text.Json;
using System.Text.Json.Serialization;

namespace Elsa.Secrets.Models;

public class CaseInsensitiveHashSetConverter : JsonConverter<HashSet<string>>
{
    public override HashSet<string> Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        if (reader.TokenType == JsonTokenType.Null)
            return new HashSet<string>(StringComparer.OrdinalIgnoreCase);

        if (reader.TokenType != JsonTokenType.StartArray)
            throw new JsonException("Expected an array of strings.");

        var values = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
        while (reader.Read())
        {
            if (reader.TokenType == JsonTokenType.EndArray)
                return values;

            if (reader.TokenType != JsonTokenType.String)
                throw new JsonException("Expected a string tag.");

            var value = reader.GetString();
            if (!string.IsNullOrWhiteSpace(value))
                values.Add(value);
        }

        throw new JsonException("Unexpected end of JSON while reading secret tags.");
    }

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