C# wpf image绑定viewModel没有显示图片

在wpf绑定图片，用viewModel的图片绑定image
我是用viewModel.cs

public class viewModel:INotifyPropertyChanged
{
#region
///代码
#endregion
public event PropertyChangedEventHandler PropertyChanged;

public BitmapImage img
{
set
{
_img= value;
OnPropertyChanged("img");
}
get
{
return _img;
}
}

private BitmapImage _img=new BitmapImage(new Uri("imgf/img.jpg" , UriKind.Relative));
//UriKind.Relative 相对

protected void OnPropertyChanged(string name)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this , new PropertyChangedEventArgs(name));
}
}

}

<Image x:Name="image" Source="{Binding Path=img}" Width="300" Height="auto" HorizontalAlignment="Center"/>

结果不会显示图，debug发现

<Image x:Name="image" Source="imgf/img.jpg" Width="300" Height="auto" HorizontalAlignment="Center"/>

显示

BitmapImage t=new BitmapImage(new Uri("imgf/img.jpg" , UriKind.Relative));
image.Source = t;

显示

image.Source=viewModel.g_viewModel().img;

不显示



想到图片位置错误，检查。

用imgf/img.jpg可以绑定image

ImageSource 和 BitmapImage可以绑定image

操作viewModel img可以xaml image