{"id":831,"date":"2008-10-17T15:59:36","date_gmt":"2008-10-17T15:59:36","guid":{"rendered":"http:\/\/osmeusapontamentos.com\/?p=831"},"modified":"2008-10-17T15:59:36","modified_gmt":"2008-10-17T15:59:36","slug":"geeky-stuff-repeaters","status":"publish","type":"post","link":"https:\/\/osmeusapontamentos.com\/index.php\/2008\/10\/17\/geeky-stuff-repeaters\/","title":{"rendered":"geeky stuff: repeaters"},"content":{"rendered":"<p>A <a href=\"http:\/\/en.wikipedia.org\/wiki\/Declarative_programming\">programa\u00e7\u00e3o declarativa<\/a> \u00e9 uma das modas actuais mas como ainda n\u00e3o estou a usar WPF e as (supostas) maravilhas do XAML limito-me a aproveitar os controles de ASP.Net que j\u00e1 existem desde a vers\u00e3o 1.0.<\/p>\n<p>Um dos controles que mais gosto \u00e9 o repeater pela facilidade com que multiplicamos texto e pelo facto de j\u00e1 incluir alguma flexibilidade no que diz respeito aquelas situa\u00e7\u00f5es habituais quando estamos numa de multiplicar texto nomedamente: ItemTemplate, AlternatingItemTemplate, FooterTemplate, HeaderTemplate e SeparatorTemplate.<\/p>\n<p>Mesmo assim por vezes surgem situa\u00e7\u00f5es que levam a que seja necess\u00e1rio um pouco de programa\u00e7\u00e3o para conseguirmos acomodar os templates \u00e0s nossas necessidades. Estou a pensar em dois cen\u00e1rios concretos: nested repeaters e repeaters sem valores.<\/p>\n<p>O caso dos nested repeaters \u00e9 aquele em que por exemplo queremos representar uma rela\u00e7\u00e3o hierarquica. Temos n registos, mas dentro que cada um desses registos ainda temos mais y que queremos apresentar. A resolu\u00e7\u00e3o do problema tem 2 partes, uma que diz respeito ao acesso a dados, a outra que diz respeito \u00e0 atribui\u00e7\u00e3o do subconjunto de informa\u00e7\u00e3o especifico que queremos mostrar no repeater de nivel inferior.<\/p>\n<p>Em rela\u00e7\u00e3o ao acesso a dados, podemos simplesmente ir buscar os dados da tabela m\u00e3e e depois por cada linha dessa tabela ir buscar os outros dados, por exemplo:<\/p>\n<div style=\"overflow:scroll\">\n<pre lang=\"vbnet\">\n    Private Sub InitRptAgrupamentos()\n\n        With rptAgrupamentos\n            .DataSource = _competenciasEngine.GetBundles()\n            .DataBind()\n        End With\n\n    End Sub\n\n    Private Sub rptAgrupamentos_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs) Handles rptAgrupamentos.ItemDataBound\n\n        Dim item As RepeaterItem = e.Item\n        Dim rpt As Repeater = CType(item.FindControl(\"rptCompetencias\"), Repeater)\n        Dim agrupamento As String = CType(item.DataItem, DataRowView).Item(\"Name\").ToString()\n\n        With rpt\n            .DataSource = _competenciasEngine.GetTags(agrupamento)\n            .DataBind()\n        End With\n\n    End Sub\n<\/pre>\n<\/div>\n<p>ou ent\u00e3o trazer as 2 tabelas de uma s\u00f3 vez e depois &#8220;dizer&#8221; qual a rela\u00e7\u00e3o que tem que ser usada para ir buscar o subconjunto correcto de dados. algo como:<\/p>\n<div style=\"overflow:scroll\">\n<pre lang=\"vb\">\n\n        ds.Tables.Add(dtUtilizadores)\n        ds.Tables.Add(dtExperiencias)\n        ds.Relations.Add(New DataRelation(\"Utilizadores_Experiencias\", dtUtilizadores.Columns(\"UserId\"), dtExperiencias.Columns(\"UserId\")))\n\n    Private Sub rptUtilizadores_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.RepeaterItemEventArgs) Handles rptUtilizadores.ItemDataBound\n\n        Dim item As RepeaterItem = e.Item\n        Dim rptExperiencias As Repeater = CType(item.FindControl(\"rptExperiencias\"), Repeater)\n\n        With rptExperiencias\n            .DataSource = CType(item.DataItem, DataRowView).CreateChildView(\"Utilizadores_Experiencias\")\n            .DataBind()\n        End With\n    End Sub\n<\/pre>\n<\/div>\n<p>mais informa\u00e7\u00e3o em: <a href=\"http:\/\/www.codeproject.com\/KB\/webforms\/Server_Nested_Repeaters.aspx\">Nesting Repeaters with Hierarchical Data and Server-Binding<\/a><\/p>\n<p>A outra situa\u00e7\u00e3o de n\u00e3o processar o repeater quando n\u00e3o h\u00e1 dados s\u00f3 \u00e9 relevante se tivermos a usar o HeaderTemplate ou FooterTemplate j\u00e1 que os outros s\u00f3 s\u00e3o processados se realmente houver dados.<br \/>\nNesse caso a solu\u00e7\u00e3o passa por verificar antes de o controlo ser renderizado se realmente h\u00e1 dados.<\/p>\n<div style=\"overflow:scroll\">\n<pre lang=\"vbnet\">\n    Protected Sub rptExperiencias_PreRender(ByVal sender As Object, ByVal e As System.EventArgs)\n\n        If CType(sender, Repeater).Items.Count = 0 Then CType(sender, Repeater).Visible = False\n\n    End Sub\n<\/pre>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>A programa\u00e7\u00e3o declarativa \u00e9 uma das modas actuais mas como ainda n\u00e3o estou a usar WPF e as (supostas) maravilhas do XAML limito-me a aproveitar os controles de ASP.Net que j\u00e1 existem desde a vers\u00e3o 1.0. Um dos controles que mais gosto \u00e9 o repeater pela facilidade com que multiplicamos texto e pelo facto de [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[70,536],"class_list":["post-831","post","type-post","status-publish","format-standard","hentry","category-ler-ver-ouvir-passear","tag-aspnet","tag-programacao"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>geeky stuff: repeaters - Os Meus Apontamentos<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/osmeusapontamentos.com\/index.php\/2008\/10\/17\/geeky-stuff-repeaters\/\" \/>\n<meta property=\"og:locale\" content=\"pt_PT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"geeky stuff: repeaters - Os Meus Apontamentos\" \/>\n<meta property=\"og:description\" content=\"A programa\u00e7\u00e3o declarativa \u00e9 uma das modas actuais mas como ainda n\u00e3o estou a usar WPF e as (supostas) maravilhas do XAML limito-me a aproveitar os controles de ASP.Net que j\u00e1 existem desde a vers\u00e3o 1.0. 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