停止列表中的重复

我有一个网格，里面有几个下拉列表，我想要的是，当用户插入新数据时，检查列表中是否已经有相同的数据。

我的代码是这样的

if(ViewState["_priceSystems"]!=null)
    _priceSystems=ViewState["_priceSystems"] as TList<PriceSystemItems>;
bool _isTrue=
    PriceSystemExist(
        _priceSystemItems.PricePlanId,
        _priceSystemItems.SurchargePlanId,
        _priceSystemItems.NoMatchAltPlanId);
if(_isTrue==false) {
    _priceSystems.Add(_priceSystemItems);
}

这里我在_priceSystems列表中添加值<>和下面的代码，我正在检查值是否存在于列表

public bool PriceSystemExist(
    int PricePlanId, int SurchagePlanId, int _noPlaneId) {
    bool isExits=false;
    if(ViewState["_priceSystems"]!=null)
        _priceSystems=ViewState["_priceSystems"] as TList<PriceSystemItems>;
    try {
        if(_priceSystems!=null) {
            foreach(PriceSystemItems item in _priceSystems) {
                if(
                    item.PricePlanId==_priceSystemItems.PriceSystemId
                    &&
                    item.ServiceTypeId==_priceSystemItems.ServiceTypeId
                    &&
                    item.NoMatchAltPlanId==_priceSystemItems.NoMatchAltPlanId) {
                    isExits=true;
                }
            }
        }
    }
    catch(Exception ex) {
    }
    return isExits;
}

我不明白我在foreach循环中检查值做错了什么。

   public bool PriceSystemExist(int PricePlanId, int SurchagePlanId, int _noPlaneId)
   {
      bool isExits = false;
      if (ViewState["_priceSystems"] != null)
      _priceSystems = ViewState["_priceSystems"] as TList<PriceSystemItems>;
    try
    {
      if(_priceSystems != null)
      {
          foreach (PriceSystemItems item in _priceSystems)
         {
            if (item.PricePlanId == PricePlanId &&  item.ServiceTypeId == SurchagePlanId && item.NoMatchAltPlanId ==  _noPlaneId)
        {
            isExits = true;
        }
     }
  }
 }
 catch (Exception ex)
 {
 }
 return isExits;
}

PricePlanId
SurchagePlanId 
_noPlaneId

_priceSystemItems.PriceSystemId
_priceSystemItems.ServiceTypeId
_priceSystemItems.NoMatchAltPlanId

foreach (PriceSystemItems item in _priceSystems)
{
        if (item.PricePlanId == PricePlanId && 
            item.ServiceTypeId == SurchagePlanId && 
            item.NoMatchAltPlanId == _noPlaneId)
        {
            isExits = true;
        }
 }