Bug 146548 [regression]Data type convert in chart data binding doesn't work.
Description: Data type convert in chart data binding doesn't work. Steps to reproduce: 1. New sample data source and dataset from OFFICES. 2. Insert a chart, bind it to dataset 3. Edit data binding to change officecode from string type to integer type 4. Drag officecode to y-series Expected result: No errors. Actual result: Unable to use a text data to render a numerical/datetime axis. org.eclipse.birt.chart.exception.ChartException at: org.eclipse.birt.chart.factory.Generator.build(Generator.java:985) org.eclipse.birt.chart.ui.swt.wizard.internal.ChartPreviewPainter.updateBuffer(ChartPreviewPainter.java:152) org.eclipse.birt.chart.ui.swt.wizard.internal.ChartPreviewPainter.renderModel(ChartPreviewPainter.java:333) org.eclipse.birt.chart.ui.swt.wizard.TaskSelectData.doLivePreview(TaskSelectData.java:1043) org.eclipse.birt.chart.ui.swt.wizard.TaskSelectData.changeTask(TaskSelectData.java:984) org.eclipse.birt.chart.ui.swt.wizard.ChartAdapter.notifyChanged(ChartAdapter.java:68) org.eclipse.emf.common.notify.impl.BasicNotifierImpl.eNotify
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/expression/ColumnReferenceExpression.java
ColumnReferenceExpression( String rowInd, String columnName )
	{
		logger.entering( ColumnReferenceExpression.class.getName( ),
				"ColumnReferenceExpression" ,columnName);
		assert( columnName != null || columnName.length() == 0 );
		m_columnName = columnName;
		m_columnIndex = -1;
		rowIndicator = rowInd; 
		logger.exiting( ColumnReferenceExpression.class.getName( ),
				"ColumnReferenceExpression" );
	}
	
	ColumnReferenceExpression( String rowInd, int columnIndex )
	{
		logger.entering( ColumnReferenceExpression.class.getName( ),
				"ColumnReferenceExpression",
				new Integer( columnIndex ) );
		assert( columnIndex >= 0 );
		m_columnIndex = columnIndex;
		rowIndicator = rowInd;
		logger.exiting( ColumnReferenceExpression.class.getName( ),
				"ColumnReferenceExpression" );
	}
	
	int getType()
	{
		return TYPE_DIRECT_COL_REF;
	}
	
	public String getColumnName( )