C# 写接口

[WebMethod(Description = "2.添加")]
public string VehicleRefuelingInsert(string json)
{
string strjson = MergeJson2(0, "失败", "");
JavaScriptSerializer js = new JavaScriptSerializer(); //实例化一个能够序列化数据的类
VehicleRefueling xmlJson1 = js.Deserialize<VehicleRefueling>(json);
DAL dal = new DAL();
string err = "";
bool bl = dal.VehicleRefuelingInsert_Dal(xmlJson1, ref err);
if (err != "")
{
return strjson = MergeJson2(0, err, "");
}
if (bl)
{
return strjson = MergeJson2(1, "", "");
}
return strjson;
}

DAL：

public bool VehicleRefuelingInsert_Dal(SmallFeature.VehicleRefueling xl, ref string err)
{
err = "";
DataSet ds = new DataSet();
try
{
#region
StringBuilder co = new StringBuilder();

xl.ConsumeOil = "0";
float ConsumeOil = (float)Math.Round(Convert.ToDecimal(xl.AddOilPrice) / Convert.ToDecimal(xl.UsingKm), 2, MidpointRounding.AwayFromZero);

co.Append(" insert into Cars_CarAddOilInfo ( ");
co.Append(" PlateNum,AllUsingKm,UsingKm,OilCardID,OilType, ");
co.Append(" OilUnitPrice,AddOilQuantity,AddOilPrice,OilCardMoney,Driver, ");
co.Append(" ConsumeOil,AddOilDate ) ");
co.Append(" values('" + xl.PlateNum + "','" + xl.AllUsingKm + "','" + xl.UsingKm + "','" + xl.OilCardID + "','" + xl.OilType + "', ");
co.Append(" '" + xl.OilUnitPrice + "','" + xl.AddOilQuantity + "','" + xl.AddOilPrice + "','" + xl.OilCardMoney + "','" + xl.Driver + "', ");
co.Append(" '" + ConsumeOil + "','" + System.DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss") + "' ) ");
int a = Insertpact(co.ToString());
if (a>0)
{
return true;
}
return false;

#endregion
}
catch (Exception ex)
{
err = ex.Message;
}
finally
{
}
return false;

}