DataSourceView 类

定义

命名空间:

System.Web.UI

程序集:

System.Web.dll

用作所有数据源视图类的基类，这些视图类定义数据源控件的功能。

public ref class DataSourceView abstract

public abstract class DataSourceView

type DataSourceView = class

Public MustInherit Class DataSourceView

继承

Object

DataSourceView

派生

System.Web.UI.WebControls.EntityDataSourceView

System.Web.UI.WebControls.ModelDataSourceView

System.Web.UI.WebControls.ObjectDataSourceView

System.Web.UI.WebControls.QueryableDataSourceView

System.Web.UI.WebControls.SiteMapDataSourceView

System.Web.UI.WebControls.SqlDataSourceView

System.Web.UI.WebControls.XmlDataSourceView

示例

下面的代码示例演示如何扩展 DataSourceView 类，以便为数据源控件创建强类型视图类。 类 CsVDataSourceView 定义数据源控件的功能 CsvDataSource ，并为数据绑定控件提供实现，以使用逗号分隔值 (.csv) 文件存储的数据。 有关数据源控件的详细信息 CsvDataSource ，请参阅 DataSourceControl 类。

// The CsvDataSourceView class encapsulates the
// capabilities of the CsvDataSource data source control.
public class CsvDataSourceView : DataSourceView
{

    public CsvDataSourceView(IDataSource owner, string name) :base(owner, DefaultViewName) {
    }

    // The data source view is named. However, the CsvDataSource
    // only supports one view, so the name is ignored, and the
    // default name used instead.
    public static string DefaultViewName = "CommaSeparatedView";

    // The location of the .csv file.
    private string sourceFile = String.Empty;
    internal string SourceFile {
        get {
            return sourceFile;
        }
        set {
            // Use MapPath when the SourceFile is set, so that files local to the
            // current directory can be easily used.
            string mappedFileName = HttpContext.Current.Server.MapPath(value);
            sourceFile = mappedFileName;
        }
    }

    // Do not add the column names as a data row. Infer columns if the CSV file does
    // not include column names.
    private bool columns = false;
    internal bool IncludesColumnNames {
        get {
            return columns;
        }
        set {
            columns = value;
        }
    }

    // Get data from the underlying data source.
    // Build and return a DataView, regardless of mode.
    protected override IEnumerable ExecuteSelect(DataSourceSelectArguments selectArgs) {
        IEnumerable dataList = null;
        // Open the .csv file.
        if (File.Exists(this.SourceFile)) {
            DataTable data = new DataTable();

            // Open the file to read from.
            using (StreamReader sr = File.OpenText(this.SourceFile)) {
                // Parse the line
                string s = "";
                string[] dataValues;
                DataColumn col;

                // Do the following to add schema.
                dataValues = sr.ReadLine().Split(',');
                // For each token in the comma-delimited string, add a column
                // to the DataTable schema.
                foreach (string token in dataValues) {
                    col = new DataColumn(token,typeof(string));
                    data.Columns.Add(col);
                }

                // Do not add the first row as data if the CSV file includes column names.
                if (! IncludesColumnNames)
                    data.Rows.Add(CopyRowData(dataValues, data.NewRow()));

                // Do the following to add data.
                while ((s = sr.ReadLine()) != null) {
                    dataValues = s.Split(',');
                    data.Rows.Add(CopyRowData(dataValues, data.NewRow()));
                }
            }
            data.AcceptChanges();
            DataView dataView = new DataView(data);
            if (!string.IsNullOrEmpty(selectArgs.SortExpression)) {
                dataView.Sort = selectArgs.SortExpression;
            }
            dataList = dataView;
        }
        else {
            throw new System.Configuration.ConfigurationErrorsException("File not found, " + this.SourceFile);
        }

        if (null == dataList) {
            throw new InvalidOperationException("No data loaded from data source.");
        }

        return dataList;
    }

    private DataRow CopyRowData(string[] source, DataRow target) {
        try {
            for (int i = 0;i < source.Length;i++) {
                target[i] = source[i];
            }
        }
        catch (System.IndexOutOfRangeException) {
            // There are more columns in this row than
            // the original schema allows.  Stop copying
            // and return the DataRow.
            return target;
        }
        return target;
    }
    // The CsvDataSourceView does not currently
    // permit deletion. You can modify or extend
    // this sample to do so.
    public override bool CanDelete {
        get {
            return false;
        }
    }
    protected override int ExecuteDelete(IDictionary keys, IDictionary values)
    {
        throw new NotSupportedException();
    }
    // The CsvDataSourceView does not currently
    // permit insertion of a new record. You can
    // modify or extend this sample to do so.
    public override bool CanInsert {
        get {
            return false;
        }
    }
    protected override int ExecuteInsert(IDictionary values)
    {
        throw new NotSupportedException();
    }
    // The CsvDataSourceView does not currently
    // permit update operations. You can modify or
    // extend this sample to do so.
    public override bool CanUpdate {
        get {
            return false;
        }
    }
    protected override int ExecuteUpdate(IDictionary keys, IDictionary values, IDictionary oldValues)
    {
        throw new NotSupportedException();
    }
}

' The CsvDataSourceView class encapsulates the
' capabilities of the CsvDataSource data source control.

Public Class CsvDataSourceView
   Inherits DataSourceView

   Public Sub New(owner As IDataSource, name As String)
       MyBase.New(owner, DefaultViewName)
   End Sub

   ' The data source view is named. However, the CsvDataSource
   ' only supports one view, so the name is ignored, and the
   ' default name used instead.
   Public Shared DefaultViewName As String = "CommaSeparatedView"

   ' The location of the .csv file.
   Private aSourceFile As String = [String].Empty

   Friend Property SourceFile() As String
      Get
         Return aSourceFile
      End Get
      Set
         ' Use MapPath when the SourceFile is set, so that files local to the
         ' current directory can be easily used.
         Dim mappedFileName As String
         mappedFileName = HttpContext.Current.Server.MapPath(value)
         aSourceFile = mappedFileName
      End Set
   End Property

   ' Do not add the column names as a data row. Infer columns if the CSV file does
   ' not include column names.
   Private columns As Boolean = False

   Friend Property IncludesColumnNames() As Boolean
      Get
         Return columns
      End Get
      Set
         columns = value
      End Set
   End Property

   ' Get data from the underlying data source.
   ' Build and return a DataView, regardless of mode.
   Protected Overrides Function ExecuteSelect(selectArgs As DataSourceSelectArguments) _
    As System.Collections.IEnumerable
      Dim dataList As IEnumerable = Nothing
      ' Open the .csv file.
      If File.Exists(Me.SourceFile) Then
         Dim data As New DataTable()

         ' Open the file to read from.
         Dim sr As StreamReader = File.OpenText(Me.SourceFile)

         Try
            ' Parse the line
            Dim dataValues() As String
            Dim col As DataColumn

            ' Do the following to add schema.
            dataValues = sr.ReadLine().Split(","c)
            ' For each token in the comma-delimited string, add a column
            ' to the DataTable schema.
            Dim token As String
            For Each token In dataValues
               col = New DataColumn(token, System.Type.GetType("System.String"))
               data.Columns.Add(col)
            Next token

            ' Do not add the first row as data if the CSV file includes column names.
            If Not IncludesColumnNames Then
               data.Rows.Add(CopyRowData(dataValues, data.NewRow()))
            End If

            ' Do the following to add data.
            Dim s As String
            Do
               s = sr.ReadLine()
               If Not s Is Nothing Then
                   dataValues = s.Split(","c)
                   data.Rows.Add(CopyRowData(dataValues, data.NewRow()))
               End If
            Loop Until s Is Nothing

         Finally
            sr.Close()
         End Try

         data.AcceptChanges()
         Dim dataView As New DataView(data)
         If Not selectArgs.SortExpression Is String.Empty Then
             dataView.Sort = selectArgs.SortExpression
         End If
         dataList = dataView
      Else
         Throw New System.Configuration.ConfigurationErrorsException("File not found, " + Me.SourceFile)
      End If

      If dataList is Nothing Then
         Throw New InvalidOperationException("No data loaded from data source.")
      End If

      Return dataList
   End Function 'ExecuteSelect


   Private Function CopyRowData([source]() As String, target As DataRow) As DataRow
      Try
         Dim i As Integer
         For i = 0 To [source].Length - 1
            target(i) = [source](i)
         Next i
      Catch iore As IndexOutOfRangeException
         ' There are more columns in this row than
         ' the original schema allows.  Stop copying
         ' and return the DataRow.
         Return target
      End Try
      Return target
   End Function 'CopyRowData

   ' The CsvDataSourceView does not currently
   ' permit deletion. You can modify or extend
   ' this sample to do so.
   Public Overrides ReadOnly Property CanDelete() As Boolean
      Get
         Return False
      End Get
   End Property

   Protected Overrides Function ExecuteDelete(keys As IDictionary, values As IDictionary) As Integer
      Throw New NotSupportedException()
   End Function 'ExecuteDelete

   ' The CsvDataSourceView does not currently
   ' permit insertion of a new record. You can
   ' modify or extend this sample to do so.
   Public Overrides ReadOnly Property CanInsert() As Boolean
      Get
         Return False
      End Get
   End Property

   Protected Overrides Function ExecuteInsert(values As IDictionary) As Integer
      Throw New NotSupportedException()
   End Function 'ExecuteInsert

   ' The CsvDataSourceView does not currently
   ' permit update operations. You can modify or
   ' extend this sample to do so.
   Public Overrides ReadOnly Property CanUpdate() As Boolean
      Get
         Return False
      End Get
   End Property

   Protected Overrides Function ExecuteUpdate(keys As IDictionary, _
                                              values As IDictionary, _
                                              oldValues As IDictionary) As Integer
      Throw New NotSupportedException()
   End Function 'ExecuteUpdate

End Class

注解

ASP.NET 支持数据绑定体系结构，该体系结构使 Web 服务器控件能够以一致的方式绑定到数据。 绑定到数据的 Web 服务器控件称为数据绑定控件，促进该绑定的类称为数据源控件。 数据源控件可以表示任何数据源：关系数据库、文件、流、业务对象等。 无论基础数据的源或格式如何，数据源控件都以一致的方式将数据呈现给数据绑定控件。

使用 ASP.NET 提供的数据源控件（包括 SqlDataSource、 AccessDataSource和 XmlDataSource）来执行大多数 Web 开发任务。 如果要实现自己的自定义数据源控件，请使用基 DataSourceControl 和 DataSourceView 类。

可以将数据源控件视为对象及其关联的数据列表（称为数据源视图）的组合 IDataSource 。 每个数据列表都由 一个 DataSourceView 对象表示。 类 DataSourceView 是与数据源控件关联的所有数据源视图或数据列表的基类。 数据源视图定义数据源控件的功能。 由于基础数据存储包含一个或多个数据列表，因此数据源控件始终与一个或多个命名数据源视图相关联。 数据源控件使用 GetViewNames 方法来枚举当前与数据源控件关联的数据源视图，并使用 GetView 方法按名称检索特定的数据源视图实例。

所有对象都 DataSourceView 支持使用 ExecuteSelect 方法从基础数据源检索数据。 所有视图（可选）都支持一组基本操作，包括 、 ExecuteInsertExecuteUpdate和 ExecuteDelete等操作。 数据绑定控件可以使用 和 GetViewNames 方法检索关联的数据源视图GetView，并在设计时或运行时查询视图，从而发现数据源控件的功能。

构造函数

DataSourceView(IDataSource, String)

初始化 DataSourceView 类的新实例。

属性

CanDelete	获取一个值，该值指示与当前 DataSourceControl 对象关联的 DataSourceView 对象是否支持 ExecuteDelete(IDictionary, IDictionary) 操作。
CanInsert	获取一个值，该值指示与当前 DataSourceControl 对象关联的 DataSourceView 对象是否支持 ExecuteInsert(IDictionary) 操作。
CanPage	获取一个值，该值指示与当前 DataSourceControl 对象关联的 DataSourceView 对象是否支持对通过 ExecuteSelect(DataSourceSelectArguments) 方法检索到的数据进行分页。
CanRetrieveTotalRowCount	获取一个值，该值指示与当前 DataSourceControl 对象关联的 DataSourceView 对象是否支持检索数据的总行数（而不是数据）。
CanSort	获取一个值，该值指示与当前 DataSourceControl 对象关联的 DataSourceView 对象是否支持基础数据源的排序视图。
CanUpdate	获取一个值，该值指示与当前 DataSourceControl 对象关联的 DataSourceView 对象是否支持 ExecuteUpdate(IDictionary, IDictionary, IDictionary) 操作。
Events	获取数据源视图的事件处理程序委托的列表。
Name	获取数据源视图的名称。

方法

CanExecute(String)	确定是否能执行指定命令。
Delete(IDictionary, IDictionary, DataSourceViewOperationCallback)	对 DataSourceView 对象所表示的数据列表执行异步删除操作。
Equals(Object)	确定指定对象是否等于当前对象。 (继承自 Object)
ExecuteCommand(String, IDictionary, IDictionary)	执行指定的命令。
ExecuteCommand(String, IDictionary, IDictionary, DataSourceViewOperationCallback)	执行指定的命令。
ExecuteDelete(IDictionary, IDictionary)	对 DataSourceView 对象所表示的数据列表执行删除操作。
ExecuteInsert(IDictionary)	对 DataSourceView 对象所表示的数据列表执行插入操作。
ExecuteSelect(DataSourceSelectArguments)	从基础数据存储获取数据列表。
ExecuteUpdate(IDictionary, IDictionary, IDictionary)	对 DataSourceView 对象所表示的数据列表执行更新操作。
GetHashCode()	作为默认哈希函数。 (继承自 Object)
GetType()	获取当前实例的 Type。 (继承自 Object)
Insert(IDictionary, DataSourceViewOperationCallback)	对 DataSourceView 对象所表示的数据列表执行异步插入操作。
MemberwiseClone()	创建当前 Object 的浅表副本。 (继承自 Object)
OnDataSourceViewChanged(EventArgs)	引发 DataSourceViewChanged 事件。
RaiseUnsupportedCapabilityError(DataSourceCapabilities)	由 RaiseUnsupportedCapabilitiesError(DataSourceView) 方法调用，用于将 ExecuteSelect(DataSourceSelectArguments) 操作所请求的功能与视图所支持的功能进行比较。
Select(DataSourceSelectArguments, DataSourceViewSelectCallback)	从基础数据存储中异步获取数据列表。
ToString()	返回表示当前对象的字符串。 (继承自 Object)
Update(IDictionary, IDictionary, IDictionary, DataSourceViewOperationCallback)	对 DataSourceView 对象所表示的数据列表执行异步更新操作。

事件

DataSourceViewChanged

在数据源视图更改时发生。

另请参阅

• DataSourceControl
• HierarchicalDataSourceView