In mvc String is null or empty is not check the null values

Question

I have Industry type in my database. When it is null, it is showing an error like:

"Nullable object must have a value."

I want my value to display empty when it is null too.

This is my code:

<p>
    <strong>Industry Type:</strong>
    <%: Model.GetIndustry(Model.IndustryId.Value).Name%>
</p>

Anyone have an idea? Please help me...

Answer 1

It is similar to "von v"'s answer, but I think the error of "Nullable object must have a value." can be from IndustryId since is nullable, so it is good to check for that first:

 <p>
    <strong>Industry Type:</strong>
    <%:if(Model.IndustryId.HasValue)
    {
      var idustry =  Model.GetIndustry(Model.IndustryId.Value);
      if(industry!= null)
        industry.Name
    }
    else
    {
    ""
    }
%>        
</p>

In my view it is good to do this

Model.GetIndustry()

in Back end, like controller, and then return the industry by viewstate, like checking in the:

string industryName = "";
     if(Industry.IndustryId.HasValue){
    var industry = YourClass.GetIndustry(Industry.IndustryId.Value);
    industryName = industry!= null ? Industry.Name : "" ;
}
ViewBag.IndustryName= industryName;

and then use your ViewBag in view like this:

<p>
    <strong>Industry Type:</strong>
    <%: ViewBag.IndustryName %>
</p>

It is good to separate the checking from view and do the logics in code.

Hope it helps.

Answer 2

Check that an industry is returned first then write the name if there's any

<%
  var industry = Model.GetIndustry(Model.IndustryId.Value);
%>

<%: industry == null ? "" : industry.Name %>

Is IndustryId nullable? Then you can do this

<%
    var industry = Model.GetIndustry(Model.IndustryId.GetValueOrDefault(0));
%>

and in the GetIndustry method, you can just return null if the id is zero.

public Industry GetIndustry(int id) {
    if (id==0) return null;
    // else do your stuff here and return a valid industry
}

Answer 3

string can accept null or empty value, why don't you try string.IsNullOrEmpty(Model.IndustryId.Value)

this is pretty self explanatory. in your controller,

  string yourValue = string.empty;
  yourValue = Model.GetIndustry(Model.IndustryId.Value).Name;

  if(string.IsNullOrEmpty(yourValue))
  {
     //display your result here!
  }

  ViewBag.IndustryValue = yourValue;

Answer 4

Please try something along the lines of

<p>
    <strong>Industry Type:</strong>
    <%: Model.IndustryId.HasValue ? Model.GetIndustry(Model.IndustryId.Value).Name : string.Empty%>
</p>

Answer 5

I found the Problem.

 <p>
    <strong>Industry Type:</strong>
    <% if (Model.IndustryId.HasValue)
      { %>
     <%: Model.GetIndustry(Model.IndustryId.Value).Name%>

     <%}
      else
      { %>
     <%:Model.IndustryId==null ? "": Model.GetIndustry(Model.IndustryId.Value).Name %>
     <%} %>
    </p>