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if (
     !(this.Department.Length == 4 && 
            "0123456789".Contains(this.Department[0]) && 
            "0123456789".Contains(this.Department[1]) && 
            "0123456789".Contains(this.Department[2]) && 
            "0123456789".Contains(this.Department[3])) &&
     !(this.Department.Length == 4 && 
            "0123456789".Contains(this.Department[0]) && 
            "ABCDEFGHIJKLMNOPQRSTUVWXYZ".Contains(this.Department[1]) && 
            "ABCDEFGHIJKLMNOPQRSTUVWXYZ".Contains(this.Department[2]) && 
            "ABCDEFGHIJKLMNOPQRSTUVWXYZ".Contains(this.Department[3])) &&
     !(this.Department.Length == 5 && 
            "0123456789".Contains(this.Department[0]) && 
            "0123456789".Contains(this.Department[4]) && 
            "ABCDEFGHIJKLMNOPQRSTUVWXYZ".Contains(this.Department[1]) && 
            "ABCDEFGHIJKLMNOPQRSTUVWXYZ".Contains(this.Department[2]) && 
            "ABCDEFGHIJKLMNOPQRSTUVWXYZ".Contains(this.Department[3])))
     {
      return "error";
     }