OrchardCMS/OrchardCore · error · ArgumentException

Invalid prefix query

Error message

Invalid prefix query

What it means

PrefixQueryProvider.CreateQuery dispatches on the JSON value kind of the query node. A prefix query must be expressed as a JSON object; any other kind (string, number, array, etc.) reaches the switch's default case and throws ArgumentException. This guards against malformed query documents.

Solutions

1. Wrap the query spec in a JSON object: {"field": {"type": "prefix", "prefix": "value"}}.
2. Check the code path producing the query JSON and ensure it emits an object for prefix queries.
3. Log/inspect the incoming query JSON to find which field node has the wrong shape.

Example fix

// before
{"Title": "Orch"}
// after
{"Title": {"type": "prefix", "prefix": "Orch"}}

if (node?.GetValueKind() == JsonValueKind.Object) { /* safe to call */ }

static bool IsPrefixQueryObject(JsonNode node) => node is JsonObject o && o.TryGetPropertyValue("type", out var t) && t.GetValueKind() == JsonValueKind.String && t.GetValue<string>() == "prefix";

try { var q = provider.CreateQuery(node); } catch (ArgumentException ex) when (ex.Message == "Invalid prefix query") { // log the raw node JSON for diagnosis }

When it happens

Trigger: Passing a query node whose value kind is not JsonValueKind.Object, e.g. {"field": "abc"} or {"field": ["a"]} where a prefix-query object is expected.

Common situations: Queries built programmatically with the wrong shape; JSON where the type discriminator object was accidentally flattened to a plain value; copy-paste errors in recipe files.

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

• Invalid term in terms query
• Invalid terms query
• Invalid wildcard query
• Invalid fuzzy query
• Invalid query

AI-assisted analysis of OrchardCMS/OrchardCore@4306c0717f (2026-09-13). Data as JSON: /api/errors/af624100ecd09183. Report an issue: GitHub.

Appendix: source

Thrown at src/OrchardCore/OrchardCore.Lucene.Core/QueryProviders/PrefixQueryProvider.cs:50

                    prefixQuery = new PrefixQuery(new Term(first.Key, value.Value<string>()));
                }
                else if (obj.TryGetPropertyValue("prefix", out var prefix))
                {
                    prefixQuery = new PrefixQuery(new Term(first.Key, prefix.Value<string>()));
                }
                else
                {
                    throw new ArgumentException("Prefix query misses prefix value");
                }

                if (obj.TryGetPropertyValue("boost", out var boost))
                {
                    prefixQuery.Boost = boost.Value<float>();
                }

                return prefixQuery;

            default: throw new ArgumentException("Invalid prefix query");
        }
    }
}

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