Below is some VBA code that shows you how to open the Item Description window from the first layer in the TOC.
Public Sub OpenItemDescription()
' Get Application
Dim pApp As IApplication
Set pApp = Application
' Get Map document
Dim pMXD As IMxDocument
Set pMXD = ThisDocument
' Get Map
Dim pmap As IMap
Set pmap = pMXD.FocusMap
' Get first layer in TOC
Dim pLayer As ILayer
Set pLayer = pmap.Layer(0)
' Get Dataset
Dim pDataset As IDataset
Set pDataset = pLayer
Dim pName As IName
Set pName = pDataset.FullName
Dim pFeatureClassName As IFeatureClassName
Set pFeatureClassName = pName
' Get Metadata for dataset
Dim pMetaData As IMetadata
Set pMetaData = pFeatureClassName
' Open window
Dim pMetadataViewWindow As IMetadataViewWindow2
Set pMetadataViewWindow = New MetadataViewWindow
With pMetadataViewWindow
Set .Application = pApp
Set .Layer = pLayer
Set .Metadata = pMetaData.Metadata
.Show True
End With
End Sub
Edit
Here is the code in c#.
private void viewMetadataButton_Click(object sender, EventArgs e)
{
IGxLayer gxLayer = new GxLayerClass();
IGxFile gxFile = gxLayer as IGxFile;
gxFile.Path = @lyrPath;
ILayer layer = gxLayer.Layer as ILayer;
IDataset pDataSet = (IDataset)layer;
IName pName = (IName)pDataSet.FullName;
IFeatureClassName pFeatureClassName = (IFeatureClassName)pName;
IMetadata pMetadata = (IMetadata)pFeatureClassName;
IMetadataViewWindow2 pMetadataViewWindow = (IMetadataViewWindow2) new MetadataViewWindow();
pMetadataViewWindow.Application = ArcMap.Application;
pMetadataViewWindow.Layer = layer;
pMetadataViewWindow.Metadata_2 = pMetadata.Metadata;
pMetadataViewWindow.Show(true);
}