如何在JavaScript中搜索null

Question

I keep on getting the error : "Value cannot be null" even if i'm checking for nulls. This is part of my code:

   <script type="text/javascript">

           if (typeof @Model.Project.ProjectPricings.Count() != 'undefined' && 
            @Model.Project.ProjectPricings.Count())
            {
            numberOfPricings = @Model.Project.ProjectPricings.Count();
            }
            sourceCodeList =  '@Html.Raw(string.Join("", Model.SourceCodeList.Select(x => "<option></option><option value=" + x.SourceCode + ">" + x.SourceCode + "</option>")))';
            targetCodeList = '@Html.Raw(string.Join("", Model.TargetCodeList.Select(x => "<option value="+ x.TargetCode + ">" + x.TargetCode + "</option>")))';
            unitTypeCodeList = '@Html.Raw(string.Join("", Model.UnitTypeCodeList.Select(x => "<option value="+ x.UnitTypeCode + ">" + x.UnitTypeCode + "</option>")))';
            currencyList = '@Html.Raw(string.Join("", Model.CurrencyList.Select(x => "<option value="+ x.CurrencyCode + ">" + x.CurrencyCode + "</option>")))';
            serviceCodeList = '@Html.Raw(string.Join("", Model.ServiceCodeList.Select(x => "<option value="+ x.ServiceCode + ">" + x.ServiceCode + "</option>")))';
            frequencyList = '@Html.Raw(string.Join("", Model.VolumeFrequencyList.Select(x => "<option value="+ x.VolumeFrequencyDescription + ">" + x.VolumeFrequencyDescription + "</option>")))';
            @*$(document)
                .ready(function() {
                    if (@Model.Project.Id == null)  {
             addPricing();
              }
              });*@
            $('#submit-price-button').button();
            $(".date").datepicker();
            $(".combobox").SumoSelect({ search: true, searchText: 'Enter here.' });

        </script>

Answer 1

By your description and the comment, my understanding is that you are having trouble when checking where @Model.Project.ProjectPricings.Count() has value, if has value set it.

your problem is you are mixing razor and javascript code for validating - in your case, it seems logical to check directly on the server side (hence razor)

so change your code to:

@if (Model.Project.ProjectPricings != null)
{
    @:numberOfPricings = @Model.Project.ProjectPricings.Count();
}

// rest same