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The SAMPR_USER_A_NAME_INFORMATION structure contains user fields.

 typedef struct _SAMPR_USER_A_NAME_INFORMATION {
   RPC_UNICODE_STRING UserName;
 } SAMPR_USER_A_NAME_INFORMATION,
  *PSAMPR_USER_A_NAME_INFORMATION;

For information on each field, see section 2.2.6.1.