Code:
/ FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / UI / WebControls / Parameter.cs / 1 / Parameter.cs
//------------------------------------------------------------------------------ //// Copyright (c) Microsoft Corporation. All rights reserved. // //----------------------------------------------------------------------------- namespace System.Web.UI.WebControls { using System; using System.Collections; using System.ComponentModel; using System.Data; using System.Diagnostics; using System.Globalization; using System.Security.Permissions; ////// Represents a parameter to a DataSourceControl. /// Parameters can be session variables, web request parameters, or of custom types. /// [ DefaultProperty("DefaultValue"), ] [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)] [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal)] public class Parameter : ICloneable, IStateManager { private ParameterCollection _owner; private bool _tracking; private StateBag _viewState; ////// Creates an instance of the Parameter class. /// public Parameter() { } ////// Creates an instance of the Parameter class with the specified parameter name. /// public Parameter(string name) { Name = name; } ////// Creates an instance of the Parameter class with the specified parameter name and type. /// public Parameter(string name, TypeCode type) { Name = name; Type = type; } ////// Creates an instance of the Parameter class with the specified parameter name, type, and default value. /// public Parameter(string name, TypeCode type, string defaultValue) { Name = name; Type = type; DefaultValue = defaultValue; } ////// Used to clone a parameter. /// protected Parameter(Parameter original) { DefaultValue = original.DefaultValue; Direction = original.Direction; Name = original.Name; ConvertEmptyStringToNull = original.ConvertEmptyStringToNull; Size = original.Size; Type = original.Type; } ////// Indicates whether the Parameter is tracking view state. /// protected bool IsTrackingViewState { get { return _tracking; } } ////// The default value to use in GetValue() if it cannot obtain a value. /// [ DefaultValue(null), WebCategory("Parameter"), WebSysDescription(SR.Parameter_DefaultValue), ] public string DefaultValue { get { object o = ViewState["DefaultValue"]; return (o as string); } set { if (DefaultValue != value) { ViewState["DefaultValue"] = value; OnParameterChanged(); } } } ////// Gets/sets the direction of the parameter. /// [ DefaultValue(ParameterDirection.Input), WebCategory("Parameter"), WebSysDescription(SR.Parameter_Direction), ] public ParameterDirection Direction { get { object o = ViewState["Direction"]; if (o == null) return ParameterDirection.Input; return (ParameterDirection)o; } set { if (Direction != value) { ViewState["Direction"] = value; OnParameterChanged(); } } } ////// Gets/sets the name of the parameter. /// [ DefaultValue(""), WebCategory("Parameter"), WebSysDescription(SR.Parameter_Name), ] public string Name { get { object o = ViewState["Name"]; if (o == null) return String.Empty; return (string)o; } set { if (Name != value) { ViewState["Name"] = value; OnParameterChanged(); } } } ////// Returns the value of parameter after converting it to the proper type. /// [ Browsable(false), ] internal object ParameterValue { get { return GetValue(ViewState["ParameterValue"], DefaultValue, Type, ConvertEmptyStringToNull, false); } } internal static object GetValue(object value, string defaultValue, TypeCode type, bool convertEmptyStringToNull, bool ignoreNullableTypeChanges) { // Convert.ChangeType() throws if you attempt to convert to DBNull, so we have to special case it. if (type == TypeCode.DBNull) { return DBNull.Value; } // Get the value and convert it to the default value if it is null if (convertEmptyStringToNull) { string stringValue = value as string; if ((stringValue != null) && (stringValue.Length == 0)) { value = null; } } if (value == null) { // Attempt to use the default value, but if it is null too, just return null immediately if (convertEmptyStringToNull && String.IsNullOrEmpty(defaultValue)) { defaultValue = null; } if (defaultValue == null) { return null; } value = defaultValue; } Debug.Assert(value != null, "Value should not be null at this point."); if (type == TypeCode.Object || type == TypeCode.Empty) { return value; } // For ObjectDataSource we special-case Nullableand do nothing because these // types will get converted when we actually call the method. if (ignoreNullableTypeChanges) { Type valueType = value.GetType(); if (valueType.IsGenericType && (valueType.GetGenericTypeDefinition() == typeof(Nullable<>))) { return value; } } return value = Convert.ChangeType(value, type, CultureInfo.CurrentCulture);; } /// /// Gets/sets the size of the parameter. /// [ DefaultValue(0), WebCategory("Parameter"), WebSysDescription(SR.Parameter_Size), ] public int Size { get { object o = ViewState["Size"]; if (o == null) return 0; return (int)o; } set { if (Size != value) { ViewState["Size"] = value; OnParameterChanged(); } } } ////// Gets/sets the type of the parameter's value. /// [ DefaultValue(TypeCode.Empty), WebCategory("Parameter"), WebSysDescription(SR.Parameter_Type), ] public TypeCode Type { get { object o = ViewState["Type"]; if (o == null) return TypeCode.Empty; return (TypeCode)o; } set { if (value < TypeCode.Empty || value > TypeCode.String) { throw new ArgumentOutOfRangeException("value"); } if (Type != value) { ViewState["Type"] = value; OnParameterChanged(); } } } ////// Gets/sets whether an empty string should be treated as a null value. If this property is set to true /// and the value is an empty string, the default value will be used. /// [ DefaultValue(true), WebCategory("Parameter"), WebSysDescription(SR.Parameter_ConvertEmptyStringToNull), ] public bool ConvertEmptyStringToNull { get { object o = ViewState["ConvertEmptyStringToNull"]; if (o == null) return true; return (bool)o; } set { if (ConvertEmptyStringToNull != value) { ViewState["ConvertEmptyStringToNull"] = value; OnParameterChanged(); } } } ////// Indicates a dictionary of state information that allows you to save and restore /// the state of a Parameter across multiple requests for the same page. /// [ Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), ] protected StateBag ViewState { get { if (_viewState == null) { _viewState = new StateBag(); if (_tracking) _viewState.TrackViewState(); } return _viewState; } } ////// Creates a new Parameter that is a copy of this Parameter. /// protected virtual Parameter Clone() { return new Parameter(this); } ////// Evaluates the parameter and returns the new value. /// The control parameter is used to access the page's framework. /// By default it returns the null, implying that the DefaultValue will /// be the value. /// protected virtual object Evaluate(HttpContext context, Control control) { return null; } ////// Loads view state. /// protected virtual void LoadViewState(object savedState) { if (savedState != null) { ViewState.LoadViewState(savedState); } } ////// Raises the ParameterChanged event. This notifies a listener that it should re-evaluate the value. /// protected void OnParameterChanged() { if (_owner != null) { _owner.CallOnParametersChanged(); } } ////// Saves view state. /// protected virtual object SaveViewState() { return (_viewState != null) ? _viewState.SaveViewState() : null; } ////// Tells the Parameter to record its entire state into view state. /// protected internal virtual void SetDirty() { ViewState.SetDirty(true); } ////// Tells the Parameter the collection it belongs to /// internal void SetOwner(ParameterCollection owner) { _owner = owner; } ////// Converts the Parameter to a string value. /// public override string ToString() { return this.Name; } ////// Tells the Parameter to start tracking property changes. /// protected virtual void TrackViewState() { _tracking = true; if (_viewState != null) { _viewState.TrackViewState(); } } ////// Updates the value of parameter. /// If the value changed, this will raise the ParametersChanged event of the ParameterCollection it belongs to. /// The control parameter is used to access the page's framework. /// internal void UpdateValue(HttpContext context, Control control) { object oldValue = ViewState["ParameterValue"]; object newValue = Evaluate(context, control); ViewState["ParameterValue"] = newValue; // If you have chains of dependency, like one control with a control parameter on another, and then a third with a control // parameter on the second, the order in which the evaluations take place is non-deterministic and may create incorrect // evaluation of parameters because all our evaluation happens during LoadComplete. The correct solution is to call DataBind // on the third control when the second control's selected value changes. Hacky, but we don't support specifying dependency // chains on data sources. if ((newValue == null && oldValue != null) || (newValue != null && !newValue.Equals(oldValue))) { OnParameterChanged(); } } #region Implementation of ICloneable ///object ICloneable.Clone() { return Clone(); } #endregion #region Implementation of IStateManager /// bool IStateManager.IsTrackingViewState { get { return IsTrackingViewState; } } /// void IStateManager.LoadViewState(object savedState) { LoadViewState(savedState); } /// object IStateManager.SaveViewState() { return SaveViewState(); } /// void IStateManager.TrackViewState() { TrackViewState(); } #endregion } }
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