UI/WebControls/Parameter.cs

//------------------------------------------------------------------------------
// <copyright file="Parameter.cs" company="Microsoft">
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
//------------------------------------------------------------------------------

namespace System.Web.UI.WebControls {

    using System;
    using System.Collections;
    using System.ComponentModel;
    using System.Data;
    using System.Diagnostics;
    using System.Globalization;


    /// <devdoc>
    /// Represents a parameter to a DataSourceControl.
    /// Parameters can be session variables, web request parameters, or of custom types.
    /// </devdoc>
    [
    DefaultProperty("DefaultValue"),
    ]
    public class Parameter : ICloneable, IStateManager {

        private ParameterCollection _owner;
        private bool _tracking;
        private StateBag _viewState;


        /// <devdoc>
        /// Creates an instance of the Parameter class.
        /// </devdoc>
        public Parameter() {
        }


        /// <devdoc>
        /// Creates an instance of the Parameter class with the specified parameter name.
        /// </devdoc>
        public Parameter(string name) {
            Name = name;
        }


        /// <devdoc>
        /// Creates an instance of the Parameter class with the specified parameter name and db type.
        /// </devdoc>
        public Parameter(string name, DbType dbType) {
            Name = name;
            DbType = dbType;
        }


        /// <devdoc>
        /// Creates an instance of the Parameter class with the specified parameter name, db type, and default value.
        /// </devdoc>
        public Parameter(string name, DbType dbType, string defaultValue) {
            Name = name;
            DbType = dbType;
            DefaultValue = defaultValue;
        }


        /// <devdoc>
        /// Creates an instance of the Parameter class with the specified parameter name and type.
        /// </devdoc>
        public Parameter(string name, TypeCode type) {
            Name = name;
            Type = type;
        }


        /// <devdoc>
        /// Creates an instance of the Parameter class with the specified parameter name, type, and default value.
        /// </devdoc>
        public Parameter(string name, TypeCode type, string defaultValue) {
            Name = name;
            Type = type;
            DefaultValue = defaultValue;
        }


        /// <devdoc>
        /// Used to clone a parameter.
        /// </devdoc>
        protected Parameter(Parameter original) {
            DefaultValue = original.DefaultValue;
            Direction = original.Direction;
            Name = original.Name;
            ConvertEmptyStringToNull = original.ConvertEmptyStringToNull;
            Size = original.Size;
            Type = original.Type;
            DbType = original.DbType;
        }


        /// <devdoc>
        /// Indicates whether the Parameter is tracking view state.
        /// </devdoc>
        protected bool IsTrackingViewState {
            get {
                return _tracking;
            }
        }


        /// <devdoc>
        /// Gets/sets the db type of the parameter's value.
        /// When DbType is DbType.Object, the Type property will be used instead
        /// </devdoc>
        [
        DefaultValue(DbType.Object),
        WebCategory("Parameter"),
        WebSysDescription(SR.Parameter_DbType),
        ]
        public DbType DbType {
            get {
                object o = ViewState["DbType"];
                if (o == null)
                    return DbType.Object;
                return (DbType)o;
            }
            set {
                if (value < DbType.AnsiString || value > DbType.DateTimeOffset) {
                    throw new ArgumentOutOfRangeException("value");
                }
                if (DbType != value) {
                    ViewState["DbType"] = value;
                    OnParameterChanged();
                }
            }
        }


        /// <devdoc>
        /// The default value to use in GetValue() if it cannot obtain a value.
        /// </devdoc>
        [
        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();
                }
            }
        }


        /// <devdoc>
        /// Gets/sets the direction of the parameter.
        /// </devdoc>
        [
        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();
                }
            }
        }


        /// <devdoc>
        /// Gets/sets the name of the parameter.
        /// </devdoc>
        [
        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();
                }
            }
        }

        /// <devdoc>
        /// Returns the value of parameter after converting it to the proper type.
        /// </devdoc>
        [
        Browsable(false),
        ]
        internal object ParameterValue {
            get {
                return GetValue(ViewState["ParameterValue"], false);
            }
        }

        public DbType GetDatabaseType() {
            DbType dbType = DbType;
            if (dbType == DbType.Object) {
                return ConvertTypeCodeToDbType(Type);
            }
            if (Type != TypeCode.Empty) {
                throw new InvalidOperationException(SR.GetString(SR.Parameter_TypeNotSupported, Name));
            }
            return dbType;
        }

        internal object GetValue(object value, bool ignoreNullableTypeChanges) {
            DbType dbType = DbType;
            if (dbType == DbType.Object) {
                return GetValue(value, DefaultValue, Type, ConvertEmptyStringToNull, ignoreNullableTypeChanges);
            }
            if (Type != TypeCode.Empty) {
                throw new InvalidOperationException(SR.GetString(SR.Parameter_TypeNotSupported, Name));
            }
            return GetValue(value, DefaultValue, dbType, ConvertEmptyStringToNull, ignoreNullableTypeChanges);
        }

        internal static object GetValue(object value, string defaultValue, DbType dbType, bool convertEmptyStringToNull,
            bool ignoreNullableTypeChanges) {

            // use the TypeCode conversion logic for Whidbey types.
            if ((dbType != DbType.DateTimeOffset) && (dbType != DbType.Time) && (dbType != DbType.Guid)) {
                TypeCode type = ConvertDbTypeToTypeCode(dbType);
                return GetValue(value, defaultValue, type, convertEmptyStringToNull, ignoreNullableTypeChanges);
            }

            value = HandleNullValue(value, defaultValue, convertEmptyStringToNull);
            if (value == null) {
                return null;
            }

            // For ObjectDataSource we special-case Nullable<T> and do nothing because these
            // types will get converted when we actually call the method.
            if (ignoreNullableTypeChanges && IsNullableType(value.GetType())) {
                return value;
            }

            if (dbType == DbType.DateTimeOffset) {
                if (value is DateTimeOffset) {
                    return value;
                }
                return DateTimeOffset.Parse(value.ToString(), CultureInfo.CurrentCulture);
            }
            else if (dbType == DbType.Time) {
                if (value is TimeSpan) {
                    return value;
                }
                return TimeSpan.Parse(value.ToString(), CultureInfo.CurrentCulture);
            }
            else if (dbType == DbType.Guid) {
                if (value is Guid) {
                    return value;
                }
                return new Guid(value.ToString());
            }

            Debug.Fail("Should never reach this point.");
            return null;
        }

        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;
            }

            value = HandleNullValue(value, defaultValue, convertEmptyStringToNull);
            if (value == null) {
                return null;
            }

            if (type == TypeCode.Object || type == TypeCode.Empty) {
                return value;
            }

            // For ObjectDataSource we special-case Nullable<T> and do nothing because these
            // types will get converted when we actually call the method.
            if (ignoreNullableTypeChanges && IsNullableType(value.GetType())) {
                return value;
            }
            return value = Convert.ChangeType(value, type, CultureInfo.CurrentCulture);;
        }

        private static object HandleNullValue(object value, string defaultValue, bool convertEmptyStringToNull) {
            // 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;
            }
            return value;
        }

        private static bool IsNullableType(Type type) {
            return type.IsGenericType && (type.GetGenericTypeDefinition() == typeof(Nullable<>));
        }

        /// <devdoc>
        /// Gets/sets the size of the parameter.
        /// </devdoc>
        [
        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();
                }
            }
        }


        /// <devdoc>
        /// Gets/sets the type of the parameter's value.
        /// </devdoc>
        [
        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();
                }
            }
        }


        /// <devdoc>
        /// 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.
        /// </devdoc>
        [
        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();
                }
            }
        }


        /// <devdoc>
        /// 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.
        /// </devdoc>
        [
        Browsable(false),
        DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
        ]
        protected StateBag ViewState {
            get {
                if (_viewState == null) {
                    _viewState = new StateBag();
                    if (_tracking)
                        _viewState.TrackViewState();
                }

                return _viewState;
            }
        }


        /// <devdoc>
        /// Creates a new Parameter that is a copy of this Parameter.
        /// </devdoc>
        protected virtual Parameter Clone() {
            return new Parameter(this);
        }


        public static TypeCode ConvertDbTypeToTypeCode(DbType dbType) {
            switch (dbType) {
                case DbType.AnsiString:
                case DbType.AnsiStringFixedLength:
                case DbType.String:
                case DbType.StringFixedLength:
                    return TypeCode.String;
                case DbType.Boolean:
                    return TypeCode.Boolean;
                case DbType.Byte:
                    return TypeCode.Byte;
                case DbType.VarNumeric:     // ???
                case DbType.Currency:
                case DbType.Decimal:
                    return TypeCode.Decimal;
                case DbType.Date:
                case DbType.DateTime:
                case DbType.DateTime2: // new Katmai type
                case DbType.Time:      // new Katmai type - no TypeCode for TimeSpan
                    return TypeCode.DateTime;
                case DbType.Double:
                    return TypeCode.Double;
                case DbType.Int16:
                    return TypeCode.Int16;
                case DbType.Int32:
                    return TypeCode.Int32;
                case DbType.Int64:
                    return TypeCode.Int64;
                case DbType.SByte:
                    return TypeCode.SByte;
                case DbType.Single:
                    return TypeCode.Single;
                case DbType.UInt16:
                    return TypeCode.UInt16;
                case DbType.UInt32:
                    return TypeCode.UInt32;
                case DbType.UInt64:
                    return TypeCode.UInt64;
                case DbType.Guid:           // ???
                case DbType.Binary:
                case DbType.Object:
                case DbType.DateTimeOffset: // new Katmai type - no TypeCode for DateTimeOffset
                default:
                    return TypeCode.Object;
            }
        }


        public static DbType ConvertTypeCodeToDbType(TypeCode typeCode) {
            // no TypeCode equivalent for TimeSpan or DateTimeOffset
            switch (typeCode) {
                case TypeCode.Boolean:
                    return DbType.Boolean;
                case TypeCode.Byte:
                    return DbType.Byte;
                case TypeCode.Char:
                    return DbType.StringFixedLength;    // ???
                case TypeCode.DateTime: // Used for Date, DateTime and DateTime2 DbTypes
                    return DbType.DateTime;
                case TypeCode.Decimal:
                    return DbType.Decimal;
                case TypeCode.Double:
                    return DbType.Double;
                case TypeCode.Int16:
                    return DbType.Int16;
                case TypeCode.Int32:
                    return DbType.Int32;
                case TypeCode.Int64:
                    return DbType.Int64;
                case TypeCode.SByte:
                    return DbType.SByte;
                case TypeCode.Single:
                    return DbType.Single;
                case TypeCode.String:
                    return DbType.String;
                case TypeCode.UInt16:
                    return DbType.UInt16;
                case TypeCode.UInt32:
                    return DbType.UInt32;
                case TypeCode.UInt64:
                    return DbType.UInt64;
                case TypeCode.DBNull:
                case TypeCode.Empty:
                case TypeCode.Object:
                default:
                    return DbType.Object;
            }
        }


        /// <devdoc>
        /// 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.
        /// </devdoc>
        protected internal virtual object Evaluate(HttpContext context, Control control) {
            return null;
        }


        /// <devdoc>
        /// Loads view state.
        /// </devdoc>
        protected virtual void LoadViewState(object savedState) {
            if (savedState != null) {
                ViewState.LoadViewState(savedState);
            }
        }


        /// <devdoc>
        /// Raises the ParameterChanged event. This notifies a listener that it should re-evaluate the value.
        /// </devdoc>
        protected void OnParameterChanged() {
            if (_owner != null) {
                _owner.CallOnParametersChanged();
            }
        }


        /// <devdoc>
        /// Saves view state.
        /// </devdoc>
        protected virtual object SaveViewState() {
            return (_viewState != null) ? _viewState.SaveViewState() : null;
        }


        /// <devdoc>
        /// Tells the Parameter to record its entire state into view state.
        /// </devdoc>
        protected internal virtual void SetDirty() {
            ViewState.SetDirty(true);
        }

        /// <devdoc>
        /// Tells the Parameter the collection it belongs to
        /// </devdoc>
        internal void SetOwner(ParameterCollection owner) {
            _owner = owner;
        }


        /// <devdoc>
        /// Converts the Parameter to a string value.
        /// </devdoc>
        public override string ToString() {
            return this.Name;
        }


        /// <devdoc>
        /// Tells the Parameter to start tracking property changes.
        /// </devdoc>
        protected virtual void TrackViewState() {
            _tracking = true;

            if (_viewState != null) {
                _viewState.TrackViewState();
            }
        }

        /// <devdoc>
        /// 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.
        /// </devdoc>
        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

        /// <internalonly/>
        object ICloneable.Clone() {
            return Clone();
        }
        #endregion


        #region Implementation of IStateManager

        /// <internalonly/>
        bool IStateManager.IsTrackingViewState {
            get {
                return IsTrackingViewState;
            }
        }


        /// <internalonly/>
        void IStateManager.LoadViewState(object savedState) {
            LoadViewState(savedState);
        }


        /// <internalonly/>
        object IStateManager.SaveViewState() {
            return SaveViewState();
        }


        /// <internalonly/>
        void IStateManager.TrackViewState() {
            TrackViewState();
        }
        #endregion
    }
}