Question

I have the following code:

var topicValue = Model.Topic;
var replaceResult = string.Empty;
if (topicValue != null & topic.Contains(topicValue)) {

}

My intent is for the if not to be executed if topicValue is null. However I am getting an error message saying:

Object reference not set to an instance of an object.

Can anyone explain how I can make this work?

Answer 1

var topicValue = Model.Topic;
var replaceResult = string.Empty;
if (topicValue != null & topic.Contains(topicValue)) {

}

Should be

var topicValue = Model.Topic;
var replaceResult = string.Empty;
if (topicValue != null && topic.Contains(topicValue)) {

}

EDIT:

Also, where do you initialise topic? Maybe you should check for that too and it should be

var topicValue = Model.Topic;
    var replaceResult = string.Empty;
    if (topicValue != null && topic != null && topic.Contains(topicValue)) {

    }