How to search and sort Templatefields on a Gridview?

Question

Basically, I have a table (Gridview) on an aspx page whose data are defined by Templatefields. For example:

<asp:GridView runat="server" ID="grdProdutos">
    <Columns>
        <asp:TemplateField HeaderText="Produto">
            <ItemTemplate>
                <asp:Label runat="server" ID="lblProduto" Text='<%# Eval("NomeProduto")%>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Tipo">
            <ItemTemplate>
                <asp:Label runat="server" ID="lblTipo" Text='<%# Eval("TipoProduto")%>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Preço">
            <ItemTemplate>
                <asp:Label runat="server" ID="lblPreco" Text='<%# Eval("PrecoProduto")%>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

The methods used in the Behind code are as follows::

RepositorioProdutos banco = new RepositorioProdutos();

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        CarregarGridView();
    }
}

public void CarregarGridView()
{
    var produtos = banco.ObterProdutos();

    if (produtos != null)
    {
        grdProdutos.DataSource = produtos;
        grdProdutos.DataBind();
    }
    else
    {
        throw new Exception("Nenhum produto encontrado.");
    }
}

I would like to know how I could implement a product search (looking for a term in any field) and how I could implement an ordering by clicking on the name of the column I would like to sort (as in Windows Explorer), without having to re-consult the bank (that is, without having to access the method banco.ObterProdutos() again).

Obs.: for the search, I am considering using a textbox that will be used to enter the keyword of the search, and a button that will trigger the search.

Answer 1

These are two different questions, in my opinion it is not as simple a task as it seems, so this answer is not intended to be definitive, but just trying to show a starting point.

About the Sorting:

Gridview has an event OnSorting that provides a parameter with a property SortExpression that contains a string normally with the name of the field to be ordered.

It turns out that with Linq we can’t sort the fields from a string, for that we need a System.Dynamic library that allows us to use strings instead of lambda Expressions.

So, install System.Linq.Dynamic library by nuget, then make sure to reference your code:

using System.Linq.Dynamic;

Now change your gridView to accept Sorting:

<asp:GridView ID="grdProdutos" AllowSorting="true" OnSorting="gridView_Sorting" runat="server">

In gridView columns we need to define the Sortexpression that tells by which fields we want to sort:

<asp:TemplateField HeaderText="Produto" SortExpression="Produto">

And in your codebehind:

protected void grdProdutos_Sorting(object sender, GridViewSortEventArgs e)
{
    var gridView = (GridView)sender;

    for (int i = 0; i < gridView.Columns.Count; i++)
        if (gridView.Columns[i].SortExpression == e.SortExpression)
            if (e.SortExpression.EndsWith(" desc"))
                gridView.Columns[i].SortExpression = e.SortExpression.Replace(" desc", "");
            else
                gridView.Columns[i].SortExpression = e.SortExpression + " desc";


    gridView.DataSource = banco.ObterProdutos().OrderBy(e.SortExpression);        
    gridView.DataBind();
}

Remembering that Dynamic Linq works with types IQueryable<T>, so if your method ObterProdutos returns a IEnumerable<T> modify the same, probably avoiding making a call to ToList().

To search you can do with the input and a stop button shoot and use the value of the input to search then set again the DataSource, for example:

gridView.DataSource = banco.ObterProdutos().Where(m => m.Produto.StartsWith(valordoinput);
gridView.DataBind();

The boring part will be keeping the search and the Sort together. You would need to create a method that fetches Sortexpression from each of the gridView columns as well as the search expression that returns a list of products with Where and OrderBy.

Answer 2

If the Grid is already populated you can use the grid ds itself to resume the information without the need to search again at the base.. I believe this would work..

 IList<seuObj> variavel = this.GridView1.DataSource as IList<seuObj>;

 if (variavel != null){
     GridView1.DataSource = variavel.OrderBy(x => x.campo).ToList();
     GridView1.DataBind();
 }