GridView Select and delete Command conflicting at row level

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.NET

Gridview

selection

.NET4.5

We are handling two scenarios in grid:
1) Doing below in row created event for firing selectIndexChanged event on row click of the grid

e.Row.Attributes.Add(AttributeOnClick, Page.ClientScript.GetPostBackEventReference(grid.Id, "Select$" + e.Row.RowIndex.ToString()));

2) Also Setting Command name for Image Button in first cell of the grid as Delete so Grid delete event fired on click of image button as below

<ItemTemplate>
                                    <ImageButton ID="imbDelete" CommandName="Delete" runat="server" SkinID="DeleteButton"
                                        ToolTip="<%$ Resources:TCMResources,242 %>" CausesValidation="false" />
                                </ItemTemplate>

all these scenarios were running fine before upgrade to .net 4.5.
but now, these are getting conflicted and delete operation is getting hanged. as after clicking delete button , select is getting fired as its part of the same row (Begin Request/End request is getting called for Select) and then(Begin request for Delete Operation)So, application getting hanged as End request not called)