BindingGroup.GetValue Method (Object, String)

Updated: July 2008

Returns the proposed value for the specified property and item.

Namespace:  System.Windows.Data
Assembly:  PresentationFramework (in PresentationFramework.dll)

public Object GetValue(
	Object item,
	string propertyName
)
You cannot use methods in XAML.

Parameters

item
Type: System.Object

The object that contains the specified property.

propertyName
Type: System.String

The property whose proposed value to get.

Return Value

Type: System.Object
The proposed property value.

ExceptionCondition
InvalidOperationException

There is not a binding for the specified item and property.

ValueUnavailableException

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 of the return value depends on the stage at which the ValidationRule occurs. For example, if a TextBox is data bound to a property of type integer and the ValidationRule that calls GetValue(Object, String) has its ValidationStep set to RawProposedValue, the method returns a string. If the ValidationRule has its ValidationStep set to ConvertedProposedValue, the method returns whatever type that is returned by the binding's converter. In this example, GetValue(Object, String) usually returns an integer.

The following example is part of an application that prompts the user to enter multiple customers and assign a sales representative to each customer. The application checks that the sales representative and the customer belong to the same region. The example shows the Validate method, which uses the GetValue(Object, String) method to get values that the customer entered. For the entire example, see Validate an Item in an ItemsControl Sample.

public class AreasMatch : ValidationRule
{
    public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)
    {
        BindingGroup bg = value as BindingGroup;
        Customer cust = bg.Items[0] as Customer;

        if (cust == null)
        {
            return new ValidationResult(false, "Customer is not the source object");
        }

        Region region = (Region)bg.GetValue(cust, "Location");
        ServiceRep rep = bg.GetValue(cust, "ServiceRepresentative") as ServiceRep;
        string customerName = bg.GetValue(cust, "Name") as string;

        if (region == rep.Area)
        {
            return ValidationResult.ValidResult;
        }
        else
        {

            StringBuilder sb = new StringBuilder();
            sb.AppendFormat("{0} must be assigned a sales representative that serves the {1} region. \n ", customerName, region);
            return new ValidationResult(false, sb.ToString());
        }
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

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

.NET Framework

Supported in: 3.5 SP1, 3.0 SP2

Date

History

Reason

July 2008

Added topic for new class.

SP1 feature change.

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