Stack overflow error in C# - but how to fix it?

Question

I've run into a really interesting runtime bug which generates a rogue stack overflow.

I've defined a structure as follows:

public enum EnumDataType { Raspberry, Orange, Pear, Apple };

public class DataRequest
{
    public long DataSize 
    { 
        get { return 0; } 
        set { DataSize = value; } 
    }

    public EnumDataType DataType  
    { 
        get { return EnumDataType.Apple; } 
        set { DataType = value; } 
    }
}

The following lines work perfectly:

DataRequest request = new DataRequest();
request.DataSize = 60;

However, when I step over the following line in code, it generates a stack overflow:

request.DataType = EnumDataType.Raspberry;

Of course, I can fix it by removing the defaults, or using auto get/set, but I need it to be both readable and writable, and return a default - any ideas?

Answer 1

As others have said, the stack overflow occurs because your property setter is just calling itself. It may be simpler to understand if you think of it as a method:

// This obviously recurses until it blows up
public void SetDataType(long value)
{
    SetDataType(value);
}

As I understand it, you're trying to create normal properties but with a default value, right?

In that case, you need backing variables which are set by the setters - and the getters should return those variables, too. It's the variables which should get default values:

private long dataSize = 0;
public long DataSize {
  get { return dataSize; }
  set { dataSize = value; }
}

private EnumDataType dataType = EnumDataType.Apple;
public EnumDataType DataType { 
  get { return dataType; }
  set { dataType = value; }
}

Alternatively, use automatic properties but set the defaults in your constructor:

public long DataSize { get; set; }
public EnumDataType DataType { get; set; }

public DataRequest()
{
    DataSize = 0; // Not really required; default anyway
    DataType = EnumDataType.Apple;
}