WPF判断控件的滚动条是否移动到了最底部

/// <summary>
/// Get a bool value indicate whether is the VerticalScrollBar at buttom
/// </summary>
/// <returns>A bool value indicate whether is the VerticalScrollBar at buttom</returns>
public bool IsVerticalScrollBarAtButtom
{
get
{
bool isAtButtom = false;

// get the vertical scroll position
double dVer = this.VerticalOffset;

//get the vertical size of the scrollable content area
double dViewport = this.ViewportHeight;

//get the vertical size of the visible content area
double dExtent = this.ExtentHeight;

if (dVer != 0)
{
if (dVer + dViewport == dExtent)
{
isAtButtom = true;
}
else
{
isAtButtom = false;
}
}
else
{
isAtButtom = false;
}

if (this.VerticalScrollBarVisibility == ScrollBarVisibility.Disabled
|| this.VerticalScrollBarVisibility == ScrollBarVisibility.Hidden)
{
isAtButtom = true;
}

return isAtButtom;
}
}