how to handle null exception if model is null , how to handle it in view in mvc?

Question

In an MVC application in the controller I use Entity Framework and LINQ. I'm storing 10 records in a variable then, binding them to the model. But if there are no records I'm getting error

Index was out of range. Must be non-negative and less than the size of the collection.

While I handled null exception in view. I'm getting compile time error

Cannot initialize implicitly typed variable with an array initializer.

View:

  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:

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());
        }
    }
}

Like you do with anything else...put a conditional or a guard clause in place. — rory.ap
– rory.ap, Commented Apr 7, 2017 at 11:48

granit · Accepted Answer · 2017-04-07 13:10:57Z

2

The problem is that the code below is recognized as Razor code while you are probably expecting it to be Javascript code:

var   myLatLng = { lat:  @Model[0].latitude.ToString(), lng: @Model[0].longitude.ToString() };

Simply add @: before the statements you want to be ignored by Razor:

@if (Model != null)
{
    @: var myLatLng = { lat:  @Model[0].latitude.ToString(), lng: @Model[0].longitude.ToString() };
}
else
{
    @: var myLatLng = { lat:0, lng:0 };
}

answered Apr 7, 2017 at 13:10

granit

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1 Comment

Krishna Mohan Over a year ago

ur code is correct but @if (Model != null) not working in my case . even though model count = 0 . its entering into this loop.unble to handle exception while model is null.

Joel Pinto Ribeiro · Accepted Answer · 2017-04-07 14:54:55Z

1

Just check if the list is > 0

@if (Model != null && Model.Count >0)

edited Apr 7, 2017 at 14:54

answered Apr 7, 2017 at 14:42

Joel Pinto Ribeiro

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