SharePoint 2013: Checking SharePoint List Field NULL Value in Code

As a general practice, we tend to check that a SharePoint list column/field isn't null before we try to set/get it (normally just a few fields), but what should we do in case we are working on an application where we have a lot of fields to check?  We can break the code into a separate class so that we can create an object to make it easier to work with. Is it typical to do something like the following for every field? Is there a better way to do this?

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// Allows AddItem operation using anonymous access 
 
private static  void AllowAnonAccess()
        {
            Console.WriteLine("Enabling Anonymous access....");
            SPWebApplication webApp = SPWebApplication.Lookup(new Uri(webAppUrl));
            webApp.ClientCallableSettings.AnonymousRestrictedTypes.Remove(typeof(Microsoft.SharePoint.SPList), "GetItems");
            webApp.ClientCallableSettings.AnonymousRestrictedTypes.Remove(typeof(Microsoft.SharePoint.SPList), "AddItem");
            webApp.Update();
            Console.WriteLine("Enabled Anonymous access!"); 
        } 
 
// Revokes Add/Get Item operation using anonymous access
        private static  void RemoveAnonAccess()
        {
            Console.WriteLine("Disabling Anonymous access....");
            SPWebApplication webApp = SPWebApplication.Lookup(new Uri(webAppUrl));
            webApp.ClientCallableSettings.AnonymousRestrictedTypes.Add(typeof(Microsoft.SharePoint.SPList), "GetItems");
            webApp.ClientCallableSettings.AnonymousRestrictedTypes.Add(typeof(Microsoft.SharePoint.SPList), "AddItem");
            webApp.Update();
            Console.WriteLine("Disabled Anonymous access!");
        }

So what are the other options you can use to perform the NULL value check for each of the fields? You can find several options of how you can perform that check below.

Use a ternary condition to get the value of a list item field (or set a default value if the field is null)

Sample code

item = list.Items[0];
var field1Value = item["fieldname1"] == null  ? String.Empty : item["fieldname1"].ToString();
var field2Value = item["fieldname2"] == null  ? false  : Boolean.Parse(item["fieldname2"].ToString());

Write extension methods for SPListItem, so that you can call them right away

Sample Code

public static  T GetValue<T>(this  SPListItem item, string fieldName) where T : class
{
                 object o = item[fieldName];
                 if (o == null || !(o is T)) return null;
                 return (T)o;
}

Validation in Javascript to see if the field value is empty

Sample code

function PreSaveAction() { var columnName = document.getElementById('<% =hdnMandatoryColumn.ClientID %>'); if  (columnName != null  && columnName.value != null) { var  column = getTagFromIdentifierAndTitle("input", "", columnName.value) if  (column.value == '') { alert(columnName.value + ' is a required field.'); return  false; } else { return true; } } }
 
function getTagFromIdentifierAndTitle(tagName, identifier, title) {
    var len = identifier.length;
    var tags = document.getElementsByTagName(tagName);
    for (var i = 0; i < tags.length; i++) {
        var tempString = tags[i].id;
        if (tags[i].title == title && (identifier == "" || tempString.indexOf(identifier) == tempString.length - len)) {
            return tags[i];
        }
    }
    return null;
}

From the above solutions, you can pick any option which best fits your requirement.

You can check the problem statement and opinions at this link.

See Also

An important place to find a huge amount of SharePoint related articles is the TechNet Wiki itself. The best entry point is SharePoint Resources on the TechNet Wiki