c# - 实例化泛型类型时出现 InvalidCastException

Question

下面的代码给了我一个 InvalidCastException，说明我不能在 foreach 循环中从源类型转换到目标类型。我尝试通过该方法传递多个不同的通用集合，但我总是收到此错误。我不知道为什么。任何帮助将不胜感激。

public static void WriteDataListToFile<T>(T dataList, string folderPath, string fileName) where T : IEnumerable, ICollection
{    
     //Check to see if file already exists
     if(!File.Exists(folderPath + fileName))
     {
         //if not, create it
         File.Create(folderPath + fileName);
     }

     using(StreamWriter sw = new StreamWriter(folderPath + fileName))
     {
         foreach(T type in dataList)
         {
             sw.WriteLine(type.ToString());
         }
     }
}

Answer 1

你 dataList应该是 IEnumerable<T>

public static void WriteDataListToFile<T>(IEnumerable<T> dataList, string folderPath, string fileName)
{
    //Check to see if file already exists
    if (!File.Exists(folderPath + fileName))
    {
        //if not, create it
        File.Create(folderPath + fileName);
    }

    using (StreamWriter sw = new StreamWriter(folderPath + fileName))
    {
        foreach (T type in dataList)
        {
            sw.WriteLine(type.ToString());
        }
    }
}