Got this error when try to get label of a taxonomy term: Object reference not set to an instance of an object

Question

I am using sp 2010. This is my custom code:

var taxField = item["Application"] as TaxonomyField;

                    if (taxField.AllowMultipleValues)
                    {
                        var fieldValue = item["Application"] as TaxonomyFieldValueCollection;
                        ApplicationValue = "";
                        foreach (var valueitem in fieldValue)
                        {
                            ApplicationValue = ApplicationValue + valueitem.Label + ",";
                        }
                    }
                    else
                    {
                        var fieldValue = item["Application"] as TaxonomyFieldValue;
                        if (fieldValue != null)
                        {
                            ApplicationValue = fieldValue.Label;
                        }
                        else
                        {
                            ApplicationValue = "";
                        }
                    }

What I am doing wrong? I checked the internal name and it is "Application"

Answer 1

When you get the "Object reference not set to an instance of an object" that means that it's expecting not null value and you give it null value. The cast that you are making is returning null.

var taxField = item["Application"] as TaxonomyField;

Since you are geting the lable of only one field "Application" you can check if it is a Multiple Value Field and you don't need to make a check.

You can cast it like this:

    string ApplicationValue="";
    TaxonomyFieldValueCollection taxFieldCollection = (TaxonomyFieldValueCollection)item["Application"];
    foreach(var value in taxFieldCollection)
    {ApplicationValue += value.Label + ","
    }
    ApplicationValue.TrimEnd(',');

If its not a taxonomy value collection then cast it as TaxonomyFieldValue and just get the label no loops.