[英]how to handle null exception if model is null , how to handle it in view in mvc?
In an MVC application in the controller I use Entity Framework and LINQ. 在控制器的MVC应用程序中,我使用实体框架和LINQ。 I'm storing 10 records in a variable then, binding them to the model.
然后,我将10条记录存储在一个变量中,并将它们绑定到模型。 But if there are no records I'm getting error
但是,如果没有记录,我会报错
Index was out of range.
索引超出范围。 Must be non-negative and less than the size of the collection.
必须为非负数并且小于集合的大小。
While I handled null exception in view. 虽然我在视图中处理了null异常。 I'm getting compile time error
我收到编译时间错误
Cannot initialize implicitly typed variable with an array initializer.
无法使用数组初始化程序初始化隐式类型的变量。
View: 视图:
function initMap() {
var labels = '12345678910';
var labelIndex = 0;
@if (Model != null)
{
var myLatLng = { lat: @Model[0].latitude.ToString(), lng: @Model[0].longitude.ToString() };
}
else
{
var myLatLng = { lat:0, lng:0};//Bharat Seva Ashram
}
Controller: 控制器:
List<AssetTrackerViewModel> model = new List<AssetTrackerViewModel>();
/// PIR 1 //RAD:DN
try
{
WebRequest req = WebRequest.Create(@"https://url");
req.Method = "GET";
req.Headers["Authorization"] = "Basic " + "pwd==";
HttpWebResponse resp = req.GetResponse() as HttpWebResponse;
var encoding = resp.CharacterSet == "" ? Encoding.UTF8 : Encoding.GetEncoding(resp.CharacterSet);
using (var stream = resp.GetResponseStream())
{
var reader = new StreamReader(stream, encoding);
var responseString = reader.ReadToEnd();
**//here "items" im getting null / empty**
var items = Pirs.Where(a => !a.dataFrame.EndsWith("AAAAAAAAAAA="))
.GroupBy(a => a.dataFrame.Substring(a.dataFrame.Length - 12))
.Select(g => g.First())
.OrderByDescending(a => a.timestamp)
.Take(10);
foreach (var item in items)
{
byte[] data = Convert.FromBase64String(item.dataFrame.ToString());
}
}
}
The problem is that the code below is recognized as Razor code while you are probably expecting it to be Javascript code: 问题在于,以下代码可能被识别为Razor代码,而您可能希望它是Javascript代码:
var myLatLng = { lat: @Model[0].latitude.ToString(), lng: @Model[0].longitude.ToString() };
Simply add @:
before the statements you want to be ignored by Razor: 只需在您想被Razor忽略的语句之前添加
@:
::
@if (Model != null)
{
@: var myLatLng = { lat: @Model[0].latitude.ToString(), lng: @Model[0].longitude.ToString() };
}
else
{
@: var myLatLng = { lat:0, lng:0 };
}
只需检查列表是否> 0
@if (Model != null && Model.Count >0)
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