如何使用一个带有空值的参数列表的C＃方法？ [英] How can I use one C# method with list of parametes with null value?

问题描述

我有4个输入值employeeid，requestnumber，startdate，enddate



i创建了一个方法，就像它返回结果基于参数i传递给它就好像我需要员工ID的结果所以我只需要通过



BindingGrid（null，null，null，employeeid）

或

BindingGrid（null，null，requestnumber，null）

或

BindingGrid（startdate，enddate，null，null）



我尝试过：

< pre lang =c＃> 
< pre> public void BindingGrid（DateTime？start，DateTime？end，int？requestnumber，string？employeeid）
 
 {
 var query = ctx.tbl.Where（x => 
 （
 x.CreatedDate.Value.Year> = start.Value.Year&& x.CreatedDate.Value.Month> = start.Value.Month&& x.CreatedDate.Value.Day> ; = start.Value.Day 
）
&& 
（
 x.CreatedDate.Value.Year< = end.Value.Year&& 
 x.CreatedDate.Value.Month< = end.Value.Month&& 
 x.CreatedDate.Value.Day< = end.Value.Day 
）
& ;&（x.resuestid = requestnumber）
 //此抛出错误：string.contains（string）的最佳重载方法匹配具有无效参数
 
&&（x.RequestorEmployeeID .Contains（employeeid）））。ToList（）; 
 gridReport.DataSource = query; 
 gridReport.DataBind（）; 
} 

解决方案

您正在使用可空类型而不检查它是否具有值：

  var  query = ctx.tbl.Where（x = >   x.CreatedDate.HasValue&&  
（x.CreatedDate.Value.Year >  = start.Value.Year && 
 x.CreatedDate.Value.Month> = start.Value.Month&& 
 x.CreatedDate.Value.Day > =start.Value.Day）&& 
（x.CreatedDate.Value.Year <  = end.Value.Year& & 
 x.CreatedDate.Value.Month <  = end.Value.Month&& 
 x.CreatedDate.Value.Day <  = end.Value.Day）&& 
（x.resuestid == requestnumber）&& 
（x。 RequestorEmployeeID.Contains（雇员）））; 

i have 4 inputs values employeeid,requestnumber,startdate,enddate

i created a method to act like it return result based on parameter i pass to it like if i need result by employee id so i just pass

BindingGrid(null,null,null, employeeid)
or
BindingGrid(null,null,requestnumber,null)
or
BindingGrid(startdate,enddate,null,null)

What I have tried:

<pre lang="c#">
<pre> public void BindingGrid(DateTime? start,DateTime? end,int? requestnumber,string? employeeid) 
    
    {
        var query = ctx.tbl.Where(x => 
(
x.CreatedDate.Value.Year >= start.Value.Year  &&                                                             x.CreatedDate.Value.Month>=start.Value.Month  &&                                                           x.CreatedDate.Value.Day  >=start.Value.Day     
)  
&&  
(
x.CreatedDate.Value.Year <= end.Value.Year &&
x.CreatedDate.Value.Month <= end.Value.Month && 
x.CreatedDate.Value.Day <= end.Value.Day 
)
&& ( x.resuestid=requestnumber)
//this throw error : best overload method match for string.contains(string) has invalid arguments  

&& ( x.RequestorEmployeeID.Contains(employeeid) ) ).ToList();
        gridReport.DataSource = query;
        gridReport.DataBind();
    }

解决方案

You are using nullable types and not checking if it has a value:

var query = ctx.tbl.Where(x => x.CreatedDate.HasValue &&
    (x.CreatedDate.Value.Year >= start.Value.Year &&
     x.CreatedDate.Value.Month>=start.Value.Month &&
     x.CreatedDate.Value.Day  >=start.Value.Day) &&
    (x.CreatedDate.Value.Year <= end.Value.Year &&
     x.CreatedDate.Value.Month <= end.Value.Month &&
     x.CreatedDate.Value.Day <= end.Value.Day) &&
    (x.resuestid == requestnumber) &&
    (x.RequestorEmployeeID.Contains(employeeid)));

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