在Web开发中,查找控件是一种常见的用户界面元素,用于从数据库中检索和显示数据。本文将介绍如何开发一个简单的查找控件,以满足特定Web项目的需求。
查找控件(Lookup Control)是一种Web用户控件,其基本思想是提供一种方式,将任何数据库表中的数据绑定到Web用户控件,以便用户友好地访问和选择数据。这种控件通常具有快速数据加载、排序、分页等功能。本文以Microsoft SQL Server数据库和Entity Framework作为后端技术,以及ASP.NET、JavaScript和jQuery作为前端技术来实现这个例子。
查找控件提供了以下属性:
查看查找控件的源代码,可以发现它非常简单易懂。它不包含复杂的逻辑,只是一些简单函数、方法和少量脚本的组合。以下是主要负责提取和显示数据的函数和方法:
''' <summary>'''
Fill HTML Table with Lookup Details.
''' </summary>'''
''' <remarks>'''
''' </remarks>'''
Private Sub FillLookUpDetails()
Dim LookUpDetails As DataTable = GetLookUpDetails()
Dim mLookupTableRows As Integer = LookUpDetails.Rows.Count
Dim DescCols As String() = Me.DescriptionColumnName.Split(","c)
Dim mLookupTableColumns As Integer = DescCols.Length + 1
Dim mLookupHeaderRow As TableHeaderRow = New TableHeaderRow()
Dim mLookupHeaderColumn As TableHeaderCell = New TableHeaderCell()
mLookupHeaderColumn.Text = Me.KeyColumnName
mLookupHeaderRow.Cells.Add(mLookupHeaderColumn)
For Each mColName As String In DescCols
mLookupHeaderColumn = New TableHeaderCell()
mLookupHeaderColumn.Text = mColName
mLookupHeaderRow.Cells.Add(mLookupHeaderColumn)
Next
LookUpData.Rows.Add(mLookupHeaderRow)
For Each mDataRow As DataRow In LookUpDetails.Rows
Dim mTableRow As TableRow = New TableRow()
Dim mTableCell As TableCell = New TableCell()
' To Find Key Column
For mTableColumn As Integer = 0 To LookUpDetails.Columns.Count - 1
mTableCell = New TableCell()
mTableCell.Text = mDataRow(mTableColumn)
mTableRow.Cells.Add(mTableCell)
Next
LookUpData.Rows.Add(mTableRow)
Next
End Sub
''' <summary>'''
Get Lookup Details from specified table.
''' </summary>'''
''' <returns>'''
''' </returns>'''
''' <remarks>'''
''' </remarks>'''
Public Function GetLookUpDetails() As DataTable
Dim mDataTable As DataTable = New DataTable()
Using mEkycContext As LookupContext = New LookupContext()
Using mDataAdapter As DbDataAdapter = New SqlDataAdapter()
mDataAdapter.SelectCommand = mEkycContext.Database.Connection.CreateCommand()
mDataAdapter.SelectCommand.CommandText = "Select " & Me.KeyColumnName & ", " & Me.DescriptionColumnName & " From " & Me.RecordTypeName
mDataTable = New DataTable()
mDataAdapter.Fill(mDataTable)
End Using
End Using
Return mDataTable
End Function
查找控件的其他功能,如搜索、分页和一些基本验证,是通过客户端脚本语言如JavaScript和jQuery来处理的。因此,与代码后端逻辑和服务器端编程相比,可以获得更快、更有效的输出。当然,这仍然是一个基本的Web用户控件,可以根据需要添加更多功能。
将查找控件集成到Web应用程序中非常简单。只需将控件文件和所需的样式和脚本文件从源代码复制到应用程序中。
<%@ Register src="LookUp.ascx" tagname="LookUp" tagprefix="uc1" %>
<uc1:LookUp ID="LookUp1" runat="server" RecordTypeName="LookupDetails" KeyColumnName="SrNo" DescriptionColumnName="Name" ShowDescription="false" DescriptionWidth="10em" AutoSearch="true" Width="3em" />
可以使用逗号(,)作为分隔符,为DescriptionColumnName属性指定多个列。例如:
<uc1:LookUp ID="LookUp1" runat="server" RecordTypeName="TableName" KeyColumnName="KeyColumn" DescriptionColumnName="Column1, Column2, Column3" ShowDescription="false" DescriptionWidth="10em" AutoSearch="true" Width="3em" />