比较无法比较C#

Question

我有一个问题，从用户输入的值与数据库进行比较。

这是可变的

List <string> onewayorigin = new List<string>();
List <string> onewaydestination = new List<string>();      
List <string> onewayterminal = new List<string>();
List <string> onewaydeparture = new List<string>();

这是我与数据库的连接，以获取值。

string strSelect;
SqlCommand cmdSelect;
SqlDataReader dtr;


SqlConnection conCust;
string connStr = ConfigurationManager.ConnectionStrings["BusConnectionString"].ConnectionString;
conCust = new SqlConnection(connStr);

strSelect = "Select * From Route";

cmdSelect = new SqlCommand(strSelect, conCust);

conCust.Open();
dtr = cmdSelect.ExecuteReader();

while (dtr.Read())
{
    onewayorigin.Add(dtr["OneWayOrigin"].ToString());
    onewaydestination.Add(dtr["OneWayDestination"].ToString());            
    onewayterminal.Add(dtr["OneWayTerminal"].ToString());   
    onewaydeparture.Add(dtr["OneWayDepartureTime"].ToString());            
}

string[] origin = onewayorigin.ToArray();
string[] destination = onewaydestination.ToArray();
string[] ow_terminal = onewayterminal.ToArray();
string[] ow_depart = onewaydeparture.ToArray();

我在这里做个比较。

if (ow_terminal.Equals(ddlterminal.SelectedValue) && ow_depart.Equals(ddlDeparture.SelectedValue))
{
    if (origin.Equals(ddlOrigin.SelectedValue) && destination.Equals(ddlDestination.SelectedValue))
    {  
        lblMessage.Text = "Record exist";
    }                
}
else
{
    lblMessage.Text = "No record exist";
}

是的，我承认我是新来的。

Answer 1

问题是您正在比较数组和字符串。因此，这将始终为您提供false。

请改用Contains。如下图所示：

if (ow_terminal.Contains(ddlterminal.SelectedValue) && ow_depart.Contains(ddlDeparture.SelectedValue))
{

    if (origin.Contains(ddlOrigin.SelectedValue) && destination.Contains(ddlDestination.SelectedValue))
    {

        lblMessage.Text = "Record exist";
    }
}
else
{
    lblMessage.Text = "No record exist";
}

Answer 2

您的比较失败，因为您正在比较一个完整的数组，只有一个值：

ow_terminal.Equals(ddlterminal.SelectedValue)
  ^ this is an array                 ^ this is properly a string

要解决此问题，您需要遍历数组以确保元素(数组中)与ddlterminal.SelectedValue中的值匹配

示例：

foreach(string terminal in ow_terminal)
{ 
  if(terminal == ddlterminal.SelectedValue)
  { 
    ...

但是，使用Contains方法可以更容易地完成此操作：

if(ow_terminal.Contains(ddlterminal.SelectedValue) && ...)

Answer 3

一旦你添加到列表中，你就需要给这些项目建立索引。因此，在进行比较时，应考虑项目索引，以便比较相应的值。您可以使用ArrayList类

ArrayList  onewayorigin = new ArrayList() ;
ArrayList  onewaydestination = new  ArrayList() ; 
ArrayList  onewayterminal = new ArrayList() ;
ArrayList  onewaydeparture = new ArrayList() ;
string strSelect;
SqlCommand cmdSelect;
SqlDataReader dtr;

SqlConnection conCust;
string connStr = ConfigurationManager.ConnectionStrings["BusConnectionString"].ConnectionString;
conCust = new SqlConnection(connStr);

strSelect = "Select * From Route";
cmdSelect = new SqlCommand(strSelect, conCust);
conCust.Open();
dtr = cmdSelect.ExecuteReader();

while (dtr.Read())
{
    i = 0;
    onewayorigin.Insert(i, dtr["OneWayOrigin"].ToString());
    onewaydestination.Insert(i, dtr["OneWayDestination"].ToString());            
    onewayterminal.Insert(i, dtr["OneWayTerminal"].ToString());   
    onewaydeparture.Insert(i, dtr["OneWayDepartureTime"].ToString());   
    i++         
}

//to compare
for (int iIndex = 0; iIndex < arr.Count; iIndex++)
{
    object o = arr[iIndex];
    if (ow_terminal[iIndex].ToString().Contains(ddlterminal.SelectedValue) &&    ow_depart[iIndex].ToString().Contains(ddlDeparture.SelectedValue))
    {

        if (onewayorigin[iIndex].ToString().Contains(ddlOrigin.SelectedValue) && destination[iIndex].ToString().Contains(ddlDestination.SelectedValue))
        {

            lblMessage.Text = "Record exist";
            return;
        }
        else
        {
            lblMessage.Text = "No record exist";
        }
    }
    else
    {
        lblMessage.Text = "No record exist";
    }
}

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