I have a method where I can only retrieve the object type at runtime. I tried to cast it to a list of known object, but I failed. 

  private string outputParamForList,c#,list,casting,enumerable,custom-object"/>
	














    

		

        

            
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首页  > 解决方案 > C# 将 Enumerable.Iterator 强制转换为已知列表 at run time

I have a method where I can only retrieve the object type at runtime. I tried to cast it to a list of known object, but I failed. 



  private string outputParamForList












c# - C# 将 Enumerable.Iterator 强制转换为已知列表 at run time

I have a method where I can only retrieve the object type at runtime. I tried to cast it to a list of known object, but I failed. 



  private string outputParamForList





问题描述



I have a method where I can only retrieve the object type at runtime. I tried to cast it to a list of known object, but I failed. 



  private string outputParamForListOrDict(IMethodReturn returnValue)
    {
        StringBuilder sb = new StringBuilder();
        String outputString = string.Empty;

        switch (returnValue.ReturnValue.GetType().GetGenericArguments()[0].Name)
        {       

            case nameof(ViewDocumentReport):

                List<ViewDocumentReport> _viewDocumentParam = (List<ViewDocumentReport>)returnValue.ReturnValue;

                //process the data here........

                return sb.ToString();

            //Other object cases

         }
    }




I got an exception below:



"Unable to cast object of type >'<TakeIterator>d__25`1[ezAcquire.RMS.Model.ViewModels.ViewDocumentReport]' to type 'System.Collections.Generic.List`1[ezAcquire.RMS.Model.ViewModels.ViewDocumentReport]'."}




I put a breakpoint in debug mode.
My returnValue.ReturnValue is of System.Linq.Enumrable.<TakeIterator>



and if I expand I can see there a list of List.



List<ViewDocumentREport>



can someone explain to me what is the d_25 meant, and advice me on how should I cast it correctly during runtime?



Thanks 







Switch Statement not running case as function


I'm trying to create a switch statement to filter through all the potential options for a filter on a table but it doesn't recognize the cases when I type anything into the search bar. I can't use an if...else statement for the filter because I need the filters to run together not one instead of the other. I've tried changing the names of the variables to make it more clear that I am designating one var per column but no such luck. Any insight would be greatly appreciated!



var Caps = event.target.value.toUpperCase();
var Hyphen = event.target.value.replace(/[-]/g, "");
var rows = document.querySelector("#Catalogue").rows;
var firstCol = rows[i].cells[0].textContent.replace(/[-]/g, '');
var thirdCol = rows[i].cells[2].textContent.replace(/[-]/g, '');
var ColOne =  rows[i].cells[0].textContent.toUpperCase();
var ColThree = rows[i].cells[2].textContent.toUpperCase();

function filterTable(event) {

for (var i = 1; i < rows.length; i++) 
{if
(switch(true){

    case (ColThree.indexOf(Caps) > -1 || thirdCol.indexOf(Hyphen) > -1):
        rows[i].style.display = ""
        break;
    case (ColOne.indexOf(Caps) > -1 || firstCol.indexOf(Hyphen) > -1):
        rows[i].style.display = "";
        break;
    case (ColOne.indexOf(Caps) > -1 && firstCol.indexOf(Hyphen) > -1):
        rows[i].style.display = "";
        break;
    case (ColThree.indexOf(Caps) > -1 && thirdCol.indexOf(Hyphen) > -1):
        rows[i].style.display = "";
    })
    else{
        rows[i].style.display = "none"
     }

   }

  }
 document.querySelector('#myInput').addEventListener('keyup', filterTable, 
  false);



标签： c#listcastingenumerablecustom-object


解决方案









如果您非常确定您的对象是您知道的类型的 IEnumerable，则可以IEnumerable<T>在执行ToList.



public class Test {

}

void Main()
{
    object x = Enumerable.Range(0,100).Select(_ => new Test()).Take(15);
    List<Test> fail = (List<Test>)x; // InvalidCastException: Unable to cast object of type '<TakeIterator>d__25`1[UserQuery+Test]' to type 'System.Collections.Generic.List`1[UserQuery+Test]'.
    List<Test> pass = ((IEnumerable<Test>)x).ToList(); // No problem
}




正如您所遇到的那样，直接从IEnumerable<T>to 转换List<T>不是有效的转换。在将其输入构造函数或使用 Linq 的方法之前，您需要object将其转换为 a 。IEnumerableList<T>ToList










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