What causes the error to occur? How to correct?
public class modelExemplo
{
public StringBuilder listNewsletter { get; set; }
}
public ActionResult funcaodeteste()
{
modelExemplo obj = new modelExemplo();
obj.listNewsletter.AppendLine("teste1");
obj.listNewsletter.AppendLine("teste2");
}
The property object needs to be initialized:
public StringBuilder listNewsletter { get; set; } = new StringBuilder();
If you use an older version of C # you need to do this in a constructor, basic example:
public modelExemplo() {
listNewsletter = new StringBuilder();
}
Declaring a variable of a type is different from instantiating an object for it. Without an existing object any operation on it will fail.
This happens because StringBuilder is a class that is not static , ie needs to be instantiated (initialized). Do this in your builder.
public class modelExemplo
{
public modelExemplo(){
listNewsletter = new StringBuilder();
}
public StringBuilder listNewsletter { get; set; }
}
listNewsletter is null, so listNewsletter.AppendLine will fire a NullReferenceException
You can correct this by initializing listNewsletter in the constructor of your class:
public class modelExemplo
{
public StringBuilder listNewsletter { get; set; }
public modelExemplo(){
listNewsletter = new StringBuilder();
}
}
I suggest you read this great topic.