弹出选择框可以选择指定类型文件的完整路径
OpenFileDialog dialog = new OpenFileDialog();
dialog.Multiselect = true;//该值确定是否可以选择多个文件
dialog.Title = "请选择文件夹";
dialog.Filter = "所有文件(*.*)|*.xlsx*";
if (dialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
string file = dialog.FileName;
this.textBox1.Text = file;
}