C#, Operator '??' cannot be applied to operands of type 'decimal' and 'decimal'
<pre><code>public decimal v1 {
  get {
    return this._v1; 
  }
  set {
    this._v1 = value ?? 0M;  // also I tried, default(decimal)
  }
}
</code></pre>

<p>Error message say : </p>

<p><strong>Operator '??' cannot be applied to operands of type 'decimal' and 'decimal'</strong></p>

<p>Why it does not work, and how should I do make it works?</p>
