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IDataSource Interface

Represents an abstract data source that data-bound controls bind to.

Namespace:  System.Web.UI
Assembly:  System.Web (in System.Web.dll)
public interface IDataSource

The IDataSource type exposes the following members.

  NameDescription
Public methodGetViewGets the named data source view associated with the data source control.
Public methodGetViewNamesGets a collection of names representing the list of view objects associated with the IDataSource interface.
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  NameDescription
Public eventDataSourceChangedOccurs when a data source control has changed in some way that affects data-bound controls.
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  NameDescription
Public Extension MethodGetDefaultValuesGets the collection of the default values for the specified data source. (Defined by DynamicDataExtensions.)
Public Extension MethodGetMetaTableGets the metadata for a table in the specified data source object. (Defined by DynamicDataExtensions.)
Public Extension MethodTryGetMetaTableDetermines whether table metadata is available. (Defined by DynamicDataExtensions.)
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ASP.NET supports a control data-binding architecture that enables Web server controls to bind to data in a consistent fashion. Web server controls that bind to data are referred to as data-bound controls, and the classes that facilitate that binding are called data source controls. Data source controls can represent any data source: a relational database, a file, a stream, a business object, and so on. Data source controls present data in a consistent way to data-bound controls, regardless of the source or format of the underlying data.

You implement the IDataSource interface when you want to implement your own custom ASP.NET data source control.

Any class that implements the IDataSource interface is a data source control. The IDataSource interface serves as the foundation for all ASP.NET data source controls and defines one of the fundamental data-binding architecture concepts with its two methods: the GetView method and the GetViewNames method. This concept is that all data source controls support one or more named views on their data. The data source view object is similar to the DataView abstraction in the System.Data namespace: a data-bindable, customized view of data for sorting, filtering, and other data operations that the view defines. At its core, a data source control does nothing more than retrieve views on data.

A data source control can have one or more associated data source view objects. Some data source controls, including those that represent relational databases such as SqlDataSource and AccessDataSource, support only one view. Other data source controls, including hierarchical data source controls such as SiteMapDataSource, support many views. The data source view defines the capabilities of a data source and the operations that it supports.

In summary, data source controls implement the IDataSource interface, support one or more named views on the data they represent, and always support data retrieval from the data source they represent. Data source controls always retrieve data on demand, such as when DataBind is called on a data bound control.

The following code example demonstrates how a class can implement the methods defined by the IDataSource interface to provide data to data-bound controls. The data source control in this example acts as a data source on a comma-separated value file, and can be used by any data-bound control to display comma-separated file data. This code example is part of a larger example provided for the DataSourceControl class.

using System;
using System.Collections;
using System.Data;
using System.IO;
using System.Security.Permissions;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

// The CsvDataSource is a data source control that retrieves its 
// data from a comma-separated value file.
[AspNetHostingPermission(SecurityAction.Demand, Level=AspNetHostingPermissionLevel.Minimal)]
public class CsvDataSource : DataSourceControl
{
    public CsvDataSource() : base() {}

    // The comma-separated value file to retrieve data from. 
    public string FileName {
        get {
            return ((CsvDataSourceView)this.GetView(String.Empty)).SourceFile;
        }
        set {
            // Only set if it is different. 
            if ( ((CsvDataSourceView)this.GetView(String.Empty)).SourceFile != value) {
                ((CsvDataSourceView)this.GetView(String.Empty)).SourceFile = value;
                RaiseDataSourceChangedEvent(EventArgs.Empty);
            }
        }
    }

    // Do not add the column names as a data row. Infer columns if the CSV file does 
    // not include column names. 
    public bool IncludesColumnNames {
        get {
            return ((CsvDataSourceView)this.GetView(String.Empty)).IncludesColumnNames;
        }
        set {
            // Only set if it is different. 
            if ( ((CsvDataSourceView)this.GetView(String.Empty)).IncludesColumnNames != value) {
                ((CsvDataSourceView)this.GetView(String.Empty)).IncludesColumnNames = value;
                RaiseDataSourceChangedEvent(EventArgs.Empty);
            }
        }
    }

    // Return a strongly typed view for the current data source control. 
    private CsvDataSourceView view = null;
    protected override DataSourceView GetView(string viewName) {
        if (null == view) {
            view = new CsvDataSourceView(this, String.Empty);
        }
        return view;
    }
    // The ListSourceHelper class calls GetList, which 
    // calls the DataSourceControl.GetViewNames method. 
    // Override the original implementation to return 
    // a collection of one element, the default view name. 
    protected override ICollection GetViewNames() {
        ArrayList al = new ArrayList(1);
        al.Add(CsvDataSourceView.DefaultViewName);
        return al as ICollection;
    }
}

// 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 (selectArgs.SortExpression != String.Empty) {
                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();
    }
}

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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