<PackageReference Include="System.Data.SqlClient" Version="4.8.1" />

Microsoft.SqlServer.Server.SqlMethodAttribute

Indicates the determinism and data access properties of a method or property on a user-defined type (UDT). The properties on the attribute reflect the physical characteristics that are used when the type is registered with SQL Server.
namespace Microsoft.SqlServer.Server { public sealed class SqlMethodAttribute : SqlFunctionAttribute { public bool InvokeIfReceiverIsNull { get; set; } public bool IsMutator { get; set; } public bool OnNullCall { get; set; } public SqlMethodAttribute(); } }