Hi Jimmer,
I performed a test based on your sample code and did see the problem.
I derive a new class named MyConverter from TypeConverter. The following is
the code in MyConverter class.
using System.ComponentModel;
public class MyConverter : TypeConverter
{
public override bool
GetStandardValuesSupported(ITypeDescriptorContext context)
{
return true;
}
public override TypeConverter.StandardValuesCollection
GetStandardValues(ITypeDescriptorContext context)
{
object myobj =
context.PropertyDescriptor.GetValue(context.Instance); //
statement3: get the current displayed object
return new StandardValuesCollection(new String[] {
"string1", "string2", "string3" });
}
}
Then I apply MyConverter to MyClass like below.
public class MyClass
{
private string name;
private int grade;
[TypeConverter(typeof(MyConverter))]
public string Name
{
get { return name;}
set { name = value;}
}
public int Grade
{
get { return grade;}
set { grade = value;}
}
}
I drag&drop a PropertyGrid onto the form and add the following code in the
form's Load event handler.
private void Form1_Load(object sender, EventArgs e)
{
MyClass ins1 = new MyClass();
ins1.Name = "this is my name";
MainClass ins2 = new MainClass();
object [] objs = {ins1,ins2};
this.propertyGrid1.SelectedObjects = objs; // statement1: add
several objects to the propertyGrid1
this.propertyGrid1.SelectedObject = ins1; // statement2:
add one object to the propertyGrid1
}
If I comment out the statement1, the statement3 in the overridden
GetStandardValues method in the MyConverter class returns the string
variable correctly when the program is running. However, if I comment out
the statement2, the statement3 returns null. I set a break point on the
statement3 and I see the type of the statement "context.Instance" is
"object[ ]" when I add several objects to the PropertyGrid. This is the
reason why the statement3 returns null in this case. We should enumerate
the elements in the array and get the current displayed objects one by one.
The following is a sample for this.
public override TypeConverter.StandardValuesCollection
GetStandardValues(ITypeDescriptorContext context)
{
if (context.Instance is object)
{
object myobj =
context.PropertyDescriptor.GetValue(context.Instance);
}
else if (context.Instance is object[])
{
for (int i = 0; i < ((object[])context.Instance).Length;
i++)
{
object myobj = ((object[])context.Instance)
;
}
}
return new StandardValuesCollection(new String[] { "string1",
"string2", "string3" });
}
Hope this helps.
If you have anything unclear or concerns, please feel free to let me know.
Sincerely,
Linda Liu
Microsoft Online Community Support
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