you could use the technique from this post Removing Columns From Gridview in List.aspx Page to filter columns by your own attributes.

Hi Steve,

I'm not sure I quite understand what you're asking.  It is possible to create new metadata attributes that your custom code can look for and act upon.  But maybe that's not what you meant?

thanks,
David

Yes thats what I meant. Then when you use

GridView1.ColumnsGenerator = new FilterDataSource(table);

as described in another post you could deal with things like:

Read/Write for Admin role
Read Only for User role
Hidden for another role

keeping the logic and the model seperate.

Yes, you absolutely could do this.  At some point, we had considered creating such security related attributes ourselves, but concluded that we could not come up with something that would please everyone.  But the system works in a way that you are encouraged to create your own custom attributes that fit your scenario.  In your generator, you can call MetaColumn.GetAttributes to get all the attributes for the column.

David

So all I need to do is create my own metadata class add the attribute to the Metadata class and then call MetaColumn.GetAttributes and it will return a collection of the attributes?

Hi David I've tried that here is my Attribute class:

using System;

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Property, AllowMultiple = true)]
public class PermissionsAttribute : System.Attribute
{
    public PermissionsAttribute(Permissions permission, String role)
    {
        this._permission = permission;
        this._role = role;
    }

    private String _role;
    public String Role
    {
        get { return this._role; }
        set { this._role = value; }
    }

    private Permissions _permission;
    public Permissions Permission
    {
        get { return this._permission; }
        set { this._permission = value; }
    }

    public enum Permissions
    {
        ReadWrite,
        ReadOnly,
        Hidden
    }
}

Here is My Metadata class

 
using System;
using System.ComponentModel.DataAnnotations;
//using NotAClue;

[MetadataType(typeof(OrderMetadata))]
public partial class Order
{
}

[Permissions(PermissionsAttribute.Permissions.ReadOnly, "User")]
[Permissions(PermissionsAttribute.Permissions.ReadWrite, "Admin")]
public class OrderMetadata
{
    [Permissions(PermissionsAttribute.Permissions.Hidden, "*")]
    [Permissions(PermissionsAttribute.Permissions.ReadWrite, "Admin")]
    public Object OrderDate { get; set; }
}
 
The problem I'm having is that if I include two attibute on the class (see above) I get the error below: 

The main type 'Order' already contains at least one attribute of type 'PermissionsAttribute'.

And if I have two attributes on the property (see above) only the first on shows in the collection.

Steve,

This is a great idea!  Much better than what I was planning to do.

Tommy

Maybe you could use an attribute per role.

[UserPermissions(ReadOnly)]

[AdminPermissions(ReadWrite)]

[DefaultPermission(Hidden)]

public Object OrderDate { get; set; }

Maybe you would define a default permissions to be set unless otherwise overridden.

Tommy

Hi Tommy that would be a workaround but I wanted somthing a bit more generic that would fit in to any pattern you wanted. Also there may be more groups than just Admin and User level of permissions e.g. Accounts, Sales, Production etc.

DynamicData is going through TypeDescriptor to get the attribute (this allows extensible attribute providers), and unfortunately it does have this restriction that it only supports one attribute of a given type.

How about reversing Tommy's idea and having one attribute type per permission instead of per role?  e.g. ReadOnlyPermission(), ReadWritePermission().  You can then make those attribute contructors take an arbitrary list of roles (by using 'params object[] roles' as the last argument).

Then you can write:

[ReadOnlyPermission("user1", "user2", "user3")]
[ReadWritePermission("admin1", "admin2")]

David

Thanks David that sounds like it will do the same.

Will this restriction always apply of one attribute of a given type?

Here are my finished attributes clsses

using System;

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Property, AllowMultiple = false)]
public class ReadWritePermissionAttribute : System.Attribute
{
    private String[] _roles;
    public ReadWritePermissionAttribute(params String[] roles)
    {
        this._roles = roles;
    }
}

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Property, AllowMultiple = false)]
public class ReadOnlyPermissionAttribute : System.Attribute
{
    private String[] _roles;
    public ReadOnlyPermissionAttribute(params String[] roles)
    {
        this._roles = roles;
    }
}

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Property, AllowMultiple = false)]
public class HiddenPermissionAttribute : System.Attribute
{
    private String[] _roles;
    public HiddenPermissionAttribute(params String[] roles)
    {
        this._roles = roles;
    }
}

Some Sample Metadata (Northwind) 

[MetadataType(typeof(OrderMetadata))]
public partial class Order
{
}

[ReadWritePermission("Admin")]
[HiddenPermission("Production")]
public class OrderMetadata
{
    [ReadWritePermission("Admin")]
    [ReadOnlyPermission("User","Accounts","Sales")]
    public Object OrderDate { get; set; }

}

And finally I can access the attribute via: 

_table.Attributes;
_table.columns[0].column.Attributes;
 
I could then iterate through the attribute collections returned turing fields or tables on or off etc.

Steve,

Using your previous example, I'm having trouble detecting the custom attribute. The below code does not work.

	public ICollection GenerateFields(Control control)
	{
		List oFields = new List();

		foreach (MetaColumn col in _table.Columns)
		{
			PermissionsAttribute a = 
				new PermissionsAttribute(PermissionsAttribute.Permissions.ReadOnly, "Admin");

			if (col.Attributes.Contains(a))
				continue;	// do anything to show it's working

			DynamicField f = new DynamicField();

			f.DataField = col.Name;
			oFields.Add(f);
		}

		return oFields;
	}

----------------------------

In the partial class:

 
[Permissions(PermissionsAttribute.Permissions.ReadOnly, "Admin")]

public object SerialNo {

get {

return _SerialNo;

}

set {

_SerialNo = value;

}

}

  

Tommy, you can't just call Attribute.Contains(a), as this will look if that exact instance of the attribute is in the collection (which it will never be).  You need to search for Attributes of that type and see if you find the one you care about.  You could write some simple heplers to make this easier.

David

If I do something silly like below, it shows the colum has 4 attributes, none of which are the custom one. I think I'm looking in the wrong place. 

Attribute: System.SerializableAttribute
Attribute: System.Runtime.CompilerServices.TypeDependencyAttribute
Attribute: System.Data.Linq.Mapping.ColumnAttribute
Attribute: System.Runtime.InteropServices.ComVisibleAttribute

		foreach (MetaColumn col in _table.Columns)
		{
			if (col.Name == "SerialNo")
			{
				string</