This error occurs when Devart .NET Standard assemblies cannot validate a license key at runtime. The guidance applies to all dotConnect providers.
After migrating a working .NET Framework application to .NET Core / .NET 6–9 and referencing NuGet packages, the error appears when opening a database connection.
Unlike the full .NET Framework, .NET Core / .NET 6–9 requires a license key to be provided at runtime. If the key is missing or invalid, .NET Standard assemblies throw: “Feature is not supported.”
Resolution
Provide the license key in the connection string using the License Key parameter:
var conn = new Devart.Data.MySql.MySqlConnection();
conn.ConnectionString = "User Id=root;Host=localhost;Database=Test;License Key=YOUR_ACTIVATION_KEY;";
conn.Open();