BindingGroup.TryGetValue(Object, String, Object) Method
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Attempts to get the proposed value for the specified property and item.
public:
bool TryGetValue(System::Object ^ item, System::String ^ propertyName, [Runtime::InteropServices::Out] System::Object ^ % value);
public bool TryGetValue (object item, string propertyName, out object value);
member this.TryGetValue : obj * string * obj -> bool
Public Function TryGetValue (item As Object, propertyName As String, ByRef value As Object) As Boolean
- item
- Object
The object that contains the specified property.
- propertyName
- String
The property whose proposed value to get.
- value
- Object
When this method returns, contains an object that represents the proposed property value. This parameter is passed uninitialized.
true
if value is the proposed value for the specified property; otherwise, false
.
The following example creates a custom ValidationRule named ValidateDateAndPrice
. In the Validate method, the example uses the TryGetValue method and the Items property to get the values the user entered into the form. Then the example checks that if an item is over 100 dollars, it will be available for at least seven days. This example is part of a larger example on the BindingGroup class
public class ValidateDateAndPrice : ValidationRule
{
// Ensure that an item over $100 is available for at least 7 days.
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
BindingGroup bg = value as BindingGroup;
// Get the source object.
PurchaseItem item = bg.Items[0] as PurchaseItem;
object doubleValue;
object dateTimeValue;
// Get the proposed values for Price and OfferExpires.
bool priceResult = bg.TryGetValue(item, "Price", out doubleValue);
bool dateResult = bg.TryGetValue(item, "OfferExpires", out dateTimeValue);
if (!priceResult || !dateResult)
{
return new ValidationResult(false, "Properties not found");
}
double price = (double)doubleValue;
DateTime offerExpires = (DateTime)dateTimeValue;
// Check that an item over $100 is available for at least 7 days.
if (price > 100)
{
if (offerExpires < DateTime.Today + new TimeSpan(7, 0, 0, 0))
{
return new ValidationResult(false, "Items over $100 must be available for at least 7 days.");
}
}
return ValidationResult.ValidResult;
}
}
Public Class ValidateDateAndPrice
Inherits ValidationRule
' Ensure that an item over $100 is available for at least 7 days.
Public Overrides Function Validate(ByVal value As Object, ByVal cultureInfo As CultureInfo) As ValidationResult
Dim bg As BindingGroup = TryCast(value, BindingGroup)
' Get the source object.
Dim item As PurchaseItem = TryCast(bg.Items(0), PurchaseItem)
Dim doubleValue As Object = Nothing
Dim dateTimeValue As Object = Nothing
' Get the proposed values for Price and OfferExpires.
Dim priceResult As Boolean = bg.TryGetValue(item, "Price", doubleValue)
Dim dateResult As Boolean = bg.TryGetValue(item, "OfferExpires", dateTimeValue)
If (Not priceResult) OrElse (Not dateResult) Then
Return New ValidationResult(False, "Properties not found")
End If
Dim price As Double = CDbl(doubleValue)
Dim offerExpires As Date = CDate(dateTimeValue)
' Check that an item over $100 is available for at least 7 days.
If price > 100 Then
If offerExpires < Date.Today + New TimeSpan(7, 0, 0, 0) Then
Return New ValidationResult(False, "Items over $100 must be available for at least 7 days.")
End If
End If
Return ValidationResult.ValidResult
End Function
End Class
TryGetValue returns false
if there is not a binding for the specified item and property or if the value of the specified property is not available, due to a conversion error or because an earlier validation rule failed.
Use this method in the ValidationRule.Validate method to get the value to be committed to the source. The type value
depends on the stage at which the ValidationRule occurs. For example, if a TextBox is data bound to a property of type integer, value
is a string if the ValidationRule that calls TryGetValue has its ValidationStep set to RawProposedValue. If the ValidationRule has its ValidationStep set to ConvertedProposedValue, the type of value
is whatever type that is returned by the binding's converter. In this example, value
is usually an integer.
Produit | Versions |
---|---|
.NET Framework | 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
Windows Desktop | 3.0, 3.1, 5, 6, 7, 8, 9 |
Commentaires sur .NET
.NET est un projet open source. Sélectionnez un lien pour fournir des commentaires :