efcore: is HasComputedColumnSql bug or wrong way to use?

Include your code

public class User:
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }

       // not want   store  this Column , but   need it    for  search  or  linq  Select Opt
        [NotMapped]
        public string FullName { get; set; }

    }
// false:   the value is computed when the value is read, and does not occupy any actual storage
  modelBuilder.Entity<User>().Property(t => t.FullName).HasComputedColumnSql("[LastName] + ' / ' + [FirstName]",false);

// want  wirte like this  
_userRepository.Where(t => t.FullName .Contains("CC")).First()

_userRepository.Select(t => t.FullName).First()

Include verbose output

Microsoft.Data.SqlClient.SqlException (0x80131904): 列名 'FullName' 无效。

Include provider and version information

EF Core version: Database provider: (e.g. Microsoft.EntityFrameworkCore.SqlServer) Target framework: (e.g. .NET 6.0) Operating system: IDE: (e.g. Visual Studio 2022)