Code for How to get the Field name value based on Lookup id value of another field in a table

public void modifiedField(FieldId _fieldId)

{

    StudentTable_S StudentT;

    switch(_fieldId)

    {

    case fieldNum(FacultyTable_s,F_StudentId):

    Select StudentT where StudentT.StudentId==this.F_StudentId;

    this.F_StudentName=StudentT.StudentName;

    break;

    default:

    break;

    }

    super(_fieldId);

}

Note: it retrieves the value of F_StudentName based on F_Id value