C# Lambda查询的正确使用
考虑以下代码:C# Lambda查询的正确使用,c#,.net,linq,lambda,C#,.net,Linq,Lambda,考虑以下代码: private static void WriteProcesses(StreamWriter sw, DateTime d) { sw.WriteLine("List of processes @ " + d.ToString()); Process[] localAll = Process.GetProcesses().Where(o => o.ProcessName.ToLower() != "svchos
private static void WriteProcesses(StreamWriter sw, DateTime d) {
sw.WriteLine("List of processes @ " + d.ToString());
Process[] localAll = Process.GetProcesses().Where(o => o.ProcessName.ToLower() != "svchost");
if(localAll.Length > 0) {
for(int i = 0; i < localAll.Length; i++) {
sw.WriteLine(" " + localAll[i].ProcessName);
}
}
}
私有静态无效写进程(StreamWriter sw,日期时间d){
sw.WriteLine(“进程列表@”+d.ToString());
Process[]localAll=Process.getprocesss()。其中(o=>o.ProcessName.ToLower()!=“svchost”);
如果(localAll.Length>0){
对于(inti=0;i
但我看到一条红色的曲线,上面写着:
无法将类型System.Collections.Generic.IEnumerable隐式转换为System.Diagnostics.Process[]。存在显式转换(是否缺少强制转换?)
我尝试将数组更改为列表,但没有成功。如果不想使用ToArray(),请将Process[]更改为var,然后将鼠标悬停在其上,查看Where语句返回的类型。(或者将鼠标悬停在Where()方法上,它会告诉您同样的事情)更改
Process[] localAll = Process.GetProcesses().Where(o => o.ProcessName.ToLower() != "svchost");
到
其中
返回一个IEnumerable
,您可以调用ToArray
将其转换为进程
类型的数组
或者,您可以通过IEnumerable
枚举返回的内容
var processes = Process.GetProcesses().Where(o => o.ProcessName.ToLower() != "svchost");
foreach (Process process in processes) {
sw.WriteLine(" " + process.ProcessName);
}
.Where方法返回IEnumerable,其中T是要筛选的类型。对于本例,您需要在Where之后调用.ToArray(),以便将集合转换为数组。我认为您最好将其作为IEnumerable处理
private static void WriteProcesses(StreamWriter sw, DateTime d) {
sw.WriteLine("List of processes @ " + d.ToString());
var localAll = Process.GetProcesses()
.Where(o => o.ProcessName.ToLower() != "svchost");
foreach(Process process in localAll) {
sw.WriteLine(" " + process.ProcessName);
}
}
我会像这样重写您的代码:
private static void WriteProcesses(StreamWriter sw, DateTime d) {
sw.WriteLine("List of processes @ " + d.ToString());
var localAll = Process.GetProcesses().Where(o => o.ProcessName.ToLower() != "svchost");
foreach(var local in localAll) {
sw.WriteLine(" " + local.ProcessName);
}
}
您的问题来自以下事实:Where
返回无法映射到数组的IEnumerable
。但是你不需要使用数组,所以我把它的用法去掉了。length
检查只是让代码对我来说不那么清晰,所以我也改成了foreach
。FYI,普遍接受的拼写是“lambda”(“lamda”有点接近希腊语,但不是公认的英语拼写)。谢谢,请记住这一点。
private static void WriteProcesses(StreamWriter sw, DateTime d) {
sw.WriteLine("List of processes @ " + d.ToString());
var localAll = Process.GetProcesses().Where(o => o.ProcessName.ToLower() != "svchost");
foreach(var local in localAll) {
sw.WriteLine(" " + local.ProcessName);
}
}