/// <summary>
/// 根据Request中的QueryString获得Linq表达式
/// </summary>
/// <typeparam name="TEntity">实体对象</typeparam>
/// <returns></returns>
protected Expression <Func <TEntity, bool> > GetExpressionFromQueryString <TEntity>()
{
Expression <Func <TEntity, bool> > expr = null;
var queryPairs = Request.GetQueryNameValuePairs().Where(q => q.Key.Equals("$format") == false);
if (queryPairs.Count() > 0)
{
var filterGroup = new FilterGroup();
foreach (var pairItem in queryPairs)
{
filterGroup.Rules.Add(new FilterRule(pairItem.Key, pairItem.Value));
}
expr = filterGroup.BuildExpression <TEntity>();
}
return(expr);
}