/// <summary>
/// Returns an expression for the Average method call which takes lambda expression as a property selctor e.g. q => q.Average(x => x.Balance) <![CDATA[ Expression<Func<IQueryable<Account>, double>> averageExpression ]]>
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="property"></param>
/// <returns></returns>
public static LambdaExpression BuildAverageExpression <T>(this string property) where T : class
{
if (property == null)
{
return(null);
}
ParameterExpression param = Expression.Parameter(typeof(IQueryable <T>), "q");
MethodCallExpression mce = param.GetAverageMethodCall(property);
Type delegateType = typeof(Func <,>).MakeGenericType(new Type[] { typeof(IQueryable <T>), typeof(T).GetMemberInfoFromFullName(property).GetMemberType() });
return(Expression.Lambda(delegateType, mce, param));
}