FDDB0021: DynamicFields property already exists

Field	Value
Code	FDDB0021
Severity	Warning

Message

Class '{0}' is marked with [EnableDynamicFields] but already has a DynamicFields property. The generated property will conflict with the existing one.

Description

When using [EnableDynamicFields], the source generator adds a DynamicFields property. If the class already has this property, there will be a conflict.

Remove the manually defined DynamicFields property and let the source generator create it, or remove the [EnableDynamicFields] attribute if you prefer to manage dynamic fields manually.

Example

The following code triggers this diagnostic:

[DynamoDbTable("nodes")]
[EnableDynamicFields]
public partial class TreeNode
{
    [PartitionKey]
    [DynamoDbAttribute("pk")]
    public string Pk { get; set; } = string.Empty;

    [SortKey]
    [DynamoDbAttribute("sk")]
    public string Sk { get; set; } = string.Empty;

    // Conflicts with the generated property
    public DynamicFieldCollection DynamicFields { get; set; } = new();
}

Fix

The corrected version:

[DynamoDbTable("nodes")]
[EnableDynamicFields]
public partial class TreeNode
{
    [PartitionKey]
    [DynamoDbAttribute("pk")]
    public string Pk { get; set; } = string.Empty;

    [SortKey]
    [DynamoDbAttribute("sk")]
    public string Sk { get; set; } = string.Empty;

    // DynamicFields property is auto-generated
}