Tips & Tricks

Re: GridViewEx

jstranger — Sun, 27 Sep 2009 07:58:10 GMT

Sounds as if your issue may be the same or related to mine - but just to check..

For several years I have used the relatively crude approach of declaring a GridView with a FooterTemplate on each column for inserts and an EmptyDataTemplate containing identical controls for inserting when there is no starting data. Then in code behind I test if the row count is 0 and if so find each control from the EmptyData template and if not do the same for the FooterRow. All works but very irritating.

I have never been interested in any crude hack such as binding to an empty DataTable. So now I am trying to build a custom GridView using the approach to override CreateChildControls broadly as set out by CISCBrain with a few slight modifications (in addition I am also autogenerating command columns but these work OK so I have removed this processing from the code below).

Protected Overrides Function CreateChildControls(ByVal dataSource As System.Collections.IEnumerable, ByVal dataBinding As Boolean) As Integer
        Dim numRows As Integer = MyBase.CreateChildControls(dataSource, dataBinding)
        If numRows = 0 And (ShowHeaderWhenEmpty Or ShowFooterWhenEmpty) Then
            Dim tab As Table = Me.CreateChildTable()
            Dim flds As DataControlField() = New DataControlField(Me.Columns.Count - 1) {}
            Me.Columns.CopyTo(flds, 0)
            If ShowHeaderWhenEmpty Then
                _headerRow = MyBase.CreateRow(-1, -1, DataControlRowType.Header, DataControlRowState.Normal)
                Me.InitializeRow(_headerRow, flds)
                tab.Rows.Add(_headerRow)
                MyBase.OnRowCreated(New GridViewRowEventArgs(_headerRow))
            End If
            If Insertable And ShowFooterWhenEmpty Then
                _footerRow = MyBase.CreateRow(-1, -1, DataControlRowType.Footer, DataControlRowState.Normal)
                Me.InitializeRow(_footerRow, flds)
                Me.ShowFooter = True
                tab.Rows.Add(_footerRow)
                MyBase.OnRowCreated(New GridViewRowEventArgs(_footerRow))
            End If
            Me.Controls.Clear()
            Me.Controls.Add(tab)
        End If
        Return numRows
    End Function

And I have the following properties:

Protected _headerRow As GridViewRow = Nothing
    Public Overloads Overrides ReadOnly Property HeaderRow() As GridViewRow
        Get
            If Not MyBase.HeaderRow Is Nothing Then
                Return MyBase.HeaderRow
            Else
                Return _headerRow
            End If
        End Get
    End Property
    Protected _footerRow As GridViewRow = Nothing
    Public Overloads Overrides ReadOnly Property FooterRow() As GridViewRow
        Get
            If Not MyBase.FooterRow Is Nothing Then
                Return MyBase.FooterRow
            Else
                Return _footerRow
            End If
        End Get
    End Property

All this works and I can retrieve values from the controls in the footer row whether there is starting data or not.

However, the problem I have is if the footer includes databound controls such as DropDownLists. In this case, I get an error that the Bind (or Eval) can only be used in the context of a databound control. This did not happen when I was using the EmptyDataTemplate for this purpose, so it would seem that somehow the footer row is not getting initialized properly. What do I need to do to ensure that the footer is properly initialized and databound? Does your code for maintaining viewstate on postbacks relate to my issue? Hopefully there is a solution which can be handled in the custom GridView class rather than requiring specific page code to initialize the footer - if the latter is the case then I am really back to square one as even the EmptyDataTemplate approach did this declaratively.

Jon

Re: GridViewEx

proturbo — Thu, 19 Feb 2009 10:19:13 GMT

Great class!

I really can't understand why MS did not implement the ability to display a footer/header when the grid is empty.

Anyway, I had problems with the GridViewEx when having input controls in the footer. They do not maintain viewstate on postbacks. Therefore I did a little tweak to solve that:

The ViewState is maintained because the footer is not the same footer as the original footer. As you can see in the code, there is newly created footer named _footerRow2. Therefore the viewstate will not be kept on postback. To fix this simply add a new readonly property exposing the _footerRow2. This way it is possible to find the controls in the new footer (using myGrid.FooterRowEmpty.findControls("NameOfInputField") and setting the values manually. If using the myGrid.FooterRow, you will find the controls, but they will of course not be visible.

Here is the code for the property:

public virtual GridViewRow FooterRowEmpty
        {
            get
            {
                if (_footerRow2 == null)
                {
                    EnsureChildControls();
                }
                return _footerRow2;
            } 
        }

And here is the usage on the footerrows:

Private Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.PreRender
        If Not grdData Is Nothing Then
            Dim footerRow As GridViewRow = grdData.FooterRow
            If grdData.Rows.Count = 0 AndAlso Not grdData.FooterRowEmpty Is Nothing Then
                footerRow = grdData.FooterRowEmpty
                LoadFilterValues(footerRow) 'Put values into the fields in the footer.
                SetDefaultButtonAndFocus(footerRow)
            ElseIf Not footerRow Is Nothing Then
                SetDefaultButtonAndFocus(footerRow)
            End If
        End If
    End Sub

This code will put the values back in the controls (LoadFilterValues) and set default button and focus (SetDefaultButtonAndFocus). You will have to write these yourself ;)

Re: GridViewEx

rohit.rokade — Mon, 16 Jun 2008 11:12:36 GMT

There is no need to do all these things if you are using Sqldatasource then just do the following thing,

1) Insert new row in sqldatasource

2) and just after that set gridview's edit index=0,

So, it will open that newly added blank row in edit mode and thats all.

Re: GridViewEx

ViagraFalls — Mon, 20 Aug 2007 09:10:46 GMT

One of them is

if (sortAttribute.IndexOf(e.SortExpression) > 0 || sortAttribute.Startswith(e.SortBLOCKED EXPRESSION

Not sure what the other one is, as I'm at work, but it's something starting with expression.

Re: GridViewEx

cruster — Thu, 16 Aug 2007 12:53:19 GMT

When using this approach to get header & footer visible when there is no record, it works. Except for one thing. If I've got a Button in the footer, its Click event will not fire. Any ideas?

Re: GridViewEx

Billyhole — Wed, 15 Aug 2007 20:43:29 GMT

Hey can you help me out? What is the correction for the "BLOCKED EXPRESSION" stuff? Thanks.

Re: GridViewEx

ViagraFalls — Tue, 07 Aug 2007 21:03:14 GMT

Doh. I think I just figured it out. Instead of creating it as a Web User Control, it helps if I create it as a Web Control Library.

Re: GridViewEx

ViagraFalls — Tue, 07 Aug 2007 20:49:16 GMT

Hmm. No matter what I tried, I could not get the code to work.

Here's what I did:

Started a new web project, created a folder called MyWebControls, and added a Web User Control to that. In the code-behind, I pasted the code code, and corrected where appropriate (The EXPRESSION BLOCKED).

Got this:

Error 1 Make sure that the class defined in this code file matches the 'inherits' attribute, and that it extends the correct base class (e.g. Page or UserControl). C:\Documents and Settings\..WebSite4\MyWebControls\GridViewExample.ascx.cs 1 33 C:\...\WebSite4\

I tried messing around in the ASPX file, by adding the MyWebControls namespace to the inherits bit:

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="GridViewExample.ascx.cs" Inherits="MyWebControls_GridViewEx" %>

At times I got this error:

Missing partial modifier on declaration of type 'GridViewExample'; another partial declaration of this type exists

Could anyone try to either give me a more detailed description of steps to take, or just specifying where I went wrong? It's been some time since I messed with ASP.NET, and I probably am overlooking something real easy. However, I have spent quite a bit of time on this already, and am hoping someone can give me a proper kick in the right direction.

Thanks!

Peter

Re: GridViewEx

ViagraFalls — Tue, 07 Aug 2007 09:23:06 GMT

The line should be:

if (sortAttribute.IndexOf(e.SortExpression) > 0 || sortAttribute.StartsWith(e.SortExpression))

Re: GridViewEx

hercules — Fri, 02 Feb 2007 21:38:20 GMT

e.SortBLOCKED EXPRESSION is undefined, it does not seem to come with the GridViewEventArgs,

let me know what the space stands for in the middle or if a function or property is missing.

Re: GridViewEx

deur_h — Mon, 20 Nov 2006 17:10:11 GMT

Hi,

I've used part of this customcontrol in the past to make a footerrow with insert functionality display/work when the gridview is empty. This has always worked great. Buttons and textboxes in the footer cuold always be used normaly when an empty gridview was encountered.

Now I've got some search functionalty embedded in the header and I'm using this customcontrol to show the gridview when it is empty.

This time it's not working though.

When an empty gridview is returned after a search has been done, the searchbutton and textboxes are shown. The sort-links returned by the GetHeader are not however. It seems the header never gets initialized properly when a search doesn't have any results. When a new search is performed after an empty search, a postback occurs, but the RowCommand is never called.

I've found that the properties HeaderText and SortExpression of the templatefield are not used when the templatefield contains a HeaderTemplate. Therefor the build-in functionality of sorting could not be used. The GetHeader function is for creating the sort-link in the header.

Because the search-textboxes are within the gridview, they do not automatically persist their value during postbacks. I've come up with a way to dynamically build and fill the filter parameters and expression and use this to persist (re-fill) the search fields.

I'm using caching and filterparameters to fill and search the data in the gridview.

My Code:

protected override int CreateChildControls:
Same as above (minus FreezeHeader, I'm using only the ShowWhenEmpty functionality)

SelectMethod (because of caching only called when necessary):
public DataSet gvOrderList_Select(string sort)
        {
            string sql = "SELECT O.*, OS.Status AS StatusNaam, K.Achternaam FROM (ORDER O LEFT JOIN OrderStatus OS ON O.Status = OS.Id) LEFT JOIN Klant K ON O.KlantId = K.Id";

            if (!string.IsNullOrEmpty(sort))
            {
                if (sort.Contains("IngangsDatum"))
                    sort = sort.Replace("IngangsDatum", "O.IngangsDatum");
                if (sort.Contains("Status"))
                    sort = sort.Replace("Status", "O.Status");
                sql += " ORDER BY " + sort + ";";
            }
            else
                sql += " ORDER BY O.IngangsDatum DESC;";

            DataSet ds = db.Select(sql);

            HttpContext.Current.Cache["CacheodsOrderList"] = ds;

            return ds;
        }

OnRowCommand:
protected void gvOrderList_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        switch (e.CommandName)
        {
            case "new":
                break;

            case "edit":
                break;

            case "del":
                break;

            case "search":
                string search;

                odsOrderList.FilterParameters.Clear();

                search = ((TextBox)gvOrderList.HeaderRow.FindControl("tbSearchOrdernummer")).Text;
                if (!string.IsNullOrEmpty(search))
                    odsOrderList.FilterParameters.Add("Ordernummer", search);
                search = ((TextBox)gvOrderList.HeaderRow.FindControl("tbSearchDatumVan")).Text;
                if (!string.IsNullOrEmpty(search))
                    odsOrderList.FilterParameters.Add("DatumVan", TypeCode.DateTime, search);
                search = ((TextBox)gvOrderList.HeaderRow.FindControl("tbSearchDatumTot")).Text;
                if (!string.IsNullOrEmpty(search))
                    odsOrderList.FilterParameters.Add("DatumTot", TypeCode.DateTime, search);
                search = ((TextBox)gvOrderList.HeaderRow.FindControl("tbSearchAchternaam")).Text;
                if (!string.IsNullOrEmpty(search))
                    odsOrderList.FilterParameters.Add("Achternaam", search);
                search = ((DropDownList)gvOrderList.HeaderRow.FindControl("ddlSearchStatus")).SelectedValue;
                if (!string.IsNullOrEmpty(search))
                    odsOrderList.FilterParameters.Add("Status", TypeCode.Int32, search);

                BuildFilterBLOCKED EXPRESSION;

                break;

            default:
                break;
        }

OnDataBound:
protected void gvOrderList_DataBound(object sender, EventArgs e)
    {
        BuildFilterBLOCKED EXPRESSION;
    }

GetHeader:
protectedstring GetHeader(string HeaderText, string SortExpression)
    {
        return "<a href=\"javascript:__doPostBack('" + gvOrderList.UniqueID + "','Sort$" + SortExpression + "')\"><font class=\"titel\">" + HeaderText + "</font></a>";
    }

BuildFilterExpression:
protected void BuildFilterBLOCKED EXPRESSION
    {
        if (odsOrderList.FilterParameters.Count > 0)
        {
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < odsOrderList.FilterParameters.Count; ++i)
            {
                switch (odsOrderList.FilterParameters[i].Name)
                {
                    case "Ordernummer":
                        ((TextBox)gvOrderList.HeaderRow.FindControl("tbSearchOrdernummer")).Text = odsOrderList.FilterParameters["Ordernummer"].DefaultValue;
                        sb.Append("Ordernummer LIKE '{" + i.ToString() + "}%' AND ");
                        break;
                    case "DatumVan":
                        ((TextBox)gvOrderList.HeaderRow.FindControl("tbSearchDatumVan")).Text = odsOrderList.FilterParameters["DatumVan"].DefaultValue;
                        sb.Append("IngangsDatum >= #{" + i.ToString() + "}# AND ");
                        break;
                    case "DatumTot":
                        ((TextBox)gvOrderList.HeaderRow.FindControl("tbSearchDatumTot")).Text = odsOrderList.FilterParameters["DatumTot"].DefaultValue;
                        sb.Append("IngangsDatum <= #{" + i.ToString() + "}# AND ");
                        break;
                    case "Achternaam":
                        ((TextBox)gvOrderList.HeaderRow.FindControl("tbSearchAchternaam")).Text = odsOrderList.FilterParameters["Achternaam"].DefaultValue;
                        sb.Append("Achternaam LIKE '{" + i.ToString() + "}%' AND ");
                        break;
                    case "Status":
                        ((DropDownList)gvOrderList.HeaderRow.FindControl("ddlSearchStatus")).SelectedIndex = Convert.ToInt32(odsOrderList.FilterParameters["Status"].DefaultValue);
                        sb.Append("Status = {" + i.ToString() + "} AND ");
                        break;
                    default:
                        break;
                }
            }
            odsOrderList.FilterExpression = (sb.Remove(sb.Length - 5, 5)).ToString();
        }
    }

Gridview:
<CustomControls:EmptyGridView ID="gvOrderList" runat="server" DataSourceID="odsOrderList" AllowSorting="true" AllowPaging="true" PageSize="10" PagerSettings-Position="Top" AutoGenerateColumns="false" ShowFooter="true" ShowHeader="true" DataKeyNames="Id" OnDataBound="gvOrderList_DataBound" OnRowCommand="gvOrderList_RowCommand" EmptyDataText="NIEUW - Geen orders" EnableViewState="false">
	<Columns>
		<asp:TemplateField>
			<HeaderTemplate>
				<asp:Button ID="btnGVSearch" runat="server" CommandName="search" TabIndex="6" Text="Zoek" CssClass="Teksten" />
			</HeaderTemplate>
			<ItemTemplate>
				<asp:ImageButton ID="ibtnEdit" runat="server" CommandName="edit" CommandArgument='<%# Eval("Id") %>' ImageUrl="~/images/edit.gif" />&nbsp;<asp:ImageButton ID="ibtnDel" runat="server" CommandName="del" CommandArgument='<%# Eval("Id") %>' OnClientClick="return confirm('Weet u zeker dat u deze order wilt verwijderen?')" ImageUrl="~/images/del.gif" />
			</ItemTemplate>
			<FooterTemplate>
				<hr width="100%" />
			</FooterTemplate>
			<HeaderStyle HorizontalAlign="Left" VerticalAlign="Bottom" />
			<ItemStyle Width="75" HorizontalAlign="Left" VerticalAlign="Top" />
		</asp:TemplateField>
		<asp:TemplateField>
			<HeaderTemplate>
				<%# GetHeader("Code", "Ordernummer") %>
				<br />
				<asp:TextBox ID="tbSearchOrdernummer" runat="server" TabIndex="1" />
			</HeaderTemplate>
			<ItemTemplate>
				<%# Eval("Ordernummer") %>
			</ItemTemplate>
			<HeaderStyle HorizontalAlign="Left" VerticalAlign="Top" />
			<ItemStyle HorizontalAlign="Left" VerticalAlign="Top" />
		</asp:TemplateField>
		...
		SOME MORE TEMPLATEFIELDS
		...
	</Columns>
</CustomControls:EmptyGridView>

<asp:ObjectDataSource ID="odsOrderList" runat="server"
TypeName="ObjectDataSources.odsOrderList"
EnableCaching="true"
CacheKeyDependency="CacheodsOrderList"
SelectMethod="gvOrderList_Select"
SortParameterName="sort"
>
</asp:ObjectDataSource>

Any light you could shed on this would be greatly appreciated.

H. Deur

Re: GridViewEx

lc_ — Thu, 19 Oct 2006 12:29:21 GMT

Hi there,

I think you would be more comfortable with a solution like

1    //create the empty row
2    GridViewRow emptyRow = new GridViewRow(-1, -1, DataControlRowType.EmptyDataRow, DataControlRowState.Normal);
3    //add row to table
4    tbl.Rows.Add(emptyRow);
5    //initialize row
6    InitializeRow(emptyRow, fields);

This way you could use the standard methods of the GridView without having to rewrite everything.

Additionaly I came up with one problem concerning the line

 1    Table table = new Table();
2    table.ID = this.ID;

I wouldn't do that, because this changes the IDs of the controls within the grid. The method of the GridView (CreateChildControls) creates the table as "ctl00" and changing the ID could cause problems on postbacks.

kind regards,

Chris

Re: GridViewEx

hansgh — Fri, 18 Aug 2006 13:53:38 GMT

Thanks, that did the trick.

I ended up rewriting it a bit so it now looks like this:

//create the empty row
GridViewRow emptyRow;
if (this.EmptyDataTemplate != null)
    emptyRow = this.Controls[0].Controls[0] as GridViewRow;
else
{
    emptyRow = new GridViewRow(-1, -1, DataControlRowType.EmptyDataRow, DataControlRowState.Normal);

    TableCell cell = new TableCell();
    cell.ColumnSpan = this.Columns.Count;
    cell.Width = Unit.Percentage(100);
    if (!String.IsNullOrEmpty(EmptyDataText))
        cell.Controls.Add(new LiteralControl(EmptyDataText));
        emptyRow.Cells.Add(cell);
}
table.Rows.Add(emptyRow);

Re: GridViewEx

CISCBrain — Thu, 17 Aug 2006 12:29:32 GMT

It's a little hackish, but should work just fine. Instead of initializing emptyRow like this:

GridViewRow emptyRow;
emptyRow = new GridViewRow(-1, -1, DataControlRowType.EmptyDataRow, DataControlRowState.Normal);
TableCell cell = new TableCell();
cell.ColumnSpan = this.Columns.Count;
cell.Width = Unit.Percentage(100);

if (!String.IsNullOrEmpty(EmptyDataText))
cell.Controls.Add(new LiteralControl(EmptyDataText));

if (this.EmptyDataTemplate != null)
EmptyDataTemplate.InstantiateIn(cell);

emptyRow.Cells.Add(cell);

Just use the already initialized row:

emptyRow = this.Controls[0].Controls[0] as GridViewRow;

The row is already initialized because of the call to base.CreateChildControls().

Re: GridViewEx

hansgh — Tue, 15 Aug 2006 19:21:10 GMT

This is a great class indeed, thanks for supplying it!

However, if I try fetching text from a code-behind function inside the EmptyDataTemplate it doesn't show the text. When debugging it enters the function and returns the text, but it doesn't get displayed. When using the asp:GridView the text shows up nicely (but of course without the header and footer).

Example:

<asp:Label id="lblNoData" runat="server" Text='<%# GetNoMessagesText() %>' SkinID="Info"></asp:Label>

</EmptyDataTemplate>

Do you have any idea why this is and if it can be fixed?