About asp Net core uses a small detail of datetime date type parameter

1.DateTime Value type ( Basic data type ), It cannot be Null, Therefore, it cannot be used as a parameter to assign a default value

[HttpGet]
public StandResult<List<Role>> Test( DateTime start = DateTime.MinValue.,DateTime end = DateTime.MaxValue)
{
                                        //DateTime As a parameter of the method , The default value cannot be set as above , This will report grammatical errors 
	........
}		

2. Don't treat DateTime Parameter to judge empty , Because when you are not DateTime When a value is passed in , It will be set by default to DateTime.MinValue

[HttpGet]
public StandResult<List<Role>> QueryRoles( DateTime start,DateTime end)
{
    
	// Don't take DateTime Carry out the empty operation , It won't be Null, If you want to use DateTime As a method parameter , Please set an initial value manually 
	if（start!=null）
		......
	if(end != null)
		......
}			

test ：

so

In some multi condition query methods , about DateTime Parameters should be treated with a small special treatment , To avoid using without passing in DateTime The default value of

[HttpGet]
public StandResult<List<Permission>> Query_Permissions([Required]int PageIndex,[Required]int PageSize,
    string name, string type, string createEmp,DateTime start,DateTime end,long Id = -1)
{
    
	// Like this method , I use two DateTime Parameter to limit the query time ,
	// According to the above situation , But it's not imported start and end date , They are all {0000-00-00....} Minimum time 
	// Bring in the query criteria , be  time>DateTime.Minvalue&&time<DateTime.Minvalue It is a paradox of time , This leads to the direct invalidation of the condition query 
    if (start == DateTime.MinValue)
        start = Convert.ToDateTime("1970-01-01");
    if (end == DateTime.MinValue)
        end = Convert.ToDateTime("9999-12-12");
        
    List<Permission> permissions = scoper.GetTool().Queryable<Permission>()
        .WhereIF(!string.IsNullOrEmpty(name), it => it.Name == name)
        .WhereIF(!string.IsNullOrEmpty(type), it => it.Type == type)
        .WhereIF(!string.IsNullOrEmpty(createEmp), it => it.Create_Emp == createEmp)
        .WhereIF(start!=null,it=>it.Create_Time>start)  // If you do not add the above initialization , When the parameter does not pass in the date type 
        .WhereIF(end != null, it => it.Create_Time < end) // Will directly use two identical minimum dates to judge , cause BUG
        .WhereIF(Id != -1, it => it.Id == Id)
        .ToPageList(PageIndex, PageSize, ref Total);
}
    

Last suggestion , The direct date parameter must be filled 【Required】 Writing can solve this problem perfectly ,（ It must be judged that the end date is greater than the start date ）