您的问题是如何在datagridview中将包含搜索结果的行置于顶部，而您当前的方法是尝试使用DataGridView.Sort直接使用UI控件。
如果您愿意用另一种方法来实现这一点，那么对于DataGridView，通过设置DataSource属性（在本例中为BindingList<Appliance>）并使用该列表通常更容易实现您想要的结果。
对于初学者来说，DGV可以完全设置使用主窗体的OnLoad中的~10行。

public partial class MainForm : Form
{
    public MainForm() => InitializeComponent();
    private BindingList<Appliance> Appliances { get; }  = new BindingList<Appliance>();
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);

        // Set up the DGV and add a few appliances.
        dtgridappliance.DataSource = Appliances;
        Appliances.Add(new Appliance(ApplianceType.Refrigerator, "Maytag" ));
        Appliances.Add(new Appliance(ApplianceType.Refrigerator, "LG" ));
        Appliances.Add(new Appliance(ApplianceType.Microwave, "Amana" ));
        Appliances.Add(new Appliance(ApplianceType.Dishwasher, "Samsung" ));
        Appliances.Add(new Appliance(ApplianceType.Dishwasher, "Whirlpool" ));
        dtgridappliance.AllowUserToAddRows = false;
        // Format columns
        dtgridappliance.Columns[nameof(Appliance.Name)].AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill;

        // Populate the combo box and dd a handler for when the combo box changes
        object[] values = Enum.GetValues(typeof(ApplianceType)).Cast<object>().ToArray();
        comboBoxSearch.Items.AddRange(values);
        comboBoxSearch.SelectedIndex = (int)ApplianceType.Refrigerator;
        comboBoxSearch.SelectionChangeCommitted += onSearchByApplianceType;
    }
}

其中表示一行数据的类如下所示：

enum ApplianceType { Dishwasher, Microwave, Refrigerator  }
class Appliance
{
    public Appliance(ApplianceType applianceType, string name)
    {
        ApplianceType = applianceType;
        Name = name;
    }
    public ApplianceType ApplianceType { get; private set; }
    public string Name { get; private set; }
}

排序需要一种方法来比较给定的Appliance和组合框中选择的类型：

private int compareToSelectedType(Appliance appliance)
{
    return appliance.ApplianceType.Equals(comboBoxSearch.SelectedItem) ?
        0 : 1; // Ones that match will sort before ones that don''t.
}

现在，当组合框更改时，您可以移除所有DataGridView项，然后以不同的顺序放回。

private void onSearchByApplianceType(object? sender, EventArgs e)
{
    // Use System.Linq to sort a new temporary list.
    var tmp = new List<Appliance>(
        Appliances
        .OrderBy(_=>compareToSelectedType(_))
        .ThenBy(_=>_.Name));

    // Remove all items from the DataGridView
    Appliances.Clear();

    // Put them back in with the new order.
    foreach (var appliance in tmp)
    {
        Appliances.Add(appliance);
    }
}

这“只是一种方法”，但我tested它和它的工作。希望这有助于让您更接近您的预期结果。