Your stored procedure returns -1 if username exists so i suggest you to return int rather than string in your Data Access Layer. here is some modifications in your code
public int SaveAdminUserAccountInformation(AdminAccountProperties oAdminUser)
{
try
{
SqlParameter[] parm = new SqlParameter[4];
parm[0] = new SqlParameter(PARM_ADMIN_USER_ID, SqlDbType.Int);
parm[0].Value = oAdminUser.UserID;
parm[1] = new SqlParameter(PARM_USER_NAME, SqlDbType.VarChar);
parm[1].Value = oAdminUser.UserName;
parm[2] = new SqlParameter(PARM_ADMIN_USER_PASSWORD, SqlDbType.VarChar);
parm[2].Value = oAdminUser.Password;
parm[3] = new SqlParameter(PARM_USER_ROLE, SqlDbType.Int);
parm[3].Value = oAdminUser.UserRole;
int a =Convert.ToInt32(SqlHelper.ExecuteScalar(this._ConnString, CommandType.StoredProcedure, SQL_ADMIN_USER_INSERT_UPDATE, parm));
return a;
}
catch (Exception ex)
{
throw ex;
}
}
after this on basis of return value do what ever you want to do in presentation layer.