asp.net c# checking error

Question

I want to check a selected date out of txtFrom and compare if that specific date exists. It should give me an alert, but it doesn't check. As a beginner I don't know if I wrote the code well, please can somebody help me? These are my codes:

string conn = WebConfigurationManager.ConnectionStrings["DIVIHOTELConnectionString"].ConnectionString;
SqlConnection myconn = new SqlConnection(conn);
SqlCommand cmd = new SqlCommand("select * from MyBooking where FromDate='" + txtFrom.Text + "'", myconn);
myconn.Open();
SqlDataReader dr = cmd.ExecuteReader();
dr.Read();
if (txtFrom.Text == dr.GetString(1))
{
    ScriptManager.RegisterStartupScript(this, GetType(), "showalert","alert('This particular date has been booked already, please select new date !');", true);
}

Learn how to use parameters. Concatenating strings (in particular with dates) is guaranteed to give wrong results at its best. And in worst case you could easily loose your whole database because you allow your user to type anything in that textbox (Sql Injection) — Steve
– Steve, Commented Oct 25, 2016 at 12:12
What is the data type of FromDate? Assuming datetime. You are doing a Select *, so what is the field order you are reading in your data reader? You should select the column names in case the schema changes. — SS_DBA
– SS_DBA, Commented Oct 25, 2016 at 12:13
And also if you are comparing with date then convert you date in C# from string to Date. — Bharat
– Bharat, Commented Oct 25, 2016 at 12:14
FromDate is varchar , shall i change to datetime and remove the*? — Gabriel Takyie
– Gabriel Takyie, Commented Oct 25, 2016 at 12:17

Jaydip Jadhav · Accepted Answer · 2016-10-25 12:40:08Z

2

It is very clear that if your query returns column in this sequence [ID] ,[ClientID] ,[RoomID] ,[Amount] ,[DateBooked] ,[IsInBook] ,[FromDate] ,[EndDate] and you accessing dr.getString(1) then this will return value for [ClientID] not for [FromDate].

Try to use exact sequence number of column so that to get work done.

if (txtFrom.Text == dr.GetString(7))
{                          ------^
     //your code here
}

answered Oct 25, 2016 at 12:40

Jaydip Jadhav

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5 Comments

Gabriel Takyie Over a year ago

but now when i write a date that doesn't exist, it gives me error

Gabriel Takyie Over a year ago

An exception of type 'System.InvalidOperationException' occurred in System.Data.dll but was not handled in user code Additional information: Invalid attempt to read when no data is present.

Jaydip Jadhav Over a year ago

Try to use dr.GetString(6). I just given sample number 7 for sequence

Gabriel Takyie Over a year ago

it worked with the 6 for an existing date but not a new date

jpaugh78 Over a year ago

Put another if statement on the outside of this one to first check if dr.GetString(6) != null

Bharat · Accepted Answer · 2016-10-25 12:30:38Z

1

My Suggestion

Check what you storing in db and what is your input date which you are comparing both are same or not, because your datatype is varchar

As per my understating you will get result when your time also match with date. likely i will say you will not get result with your current scenario.

edited Oct 25, 2016 at 12:30

answered Oct 25, 2016 at 12:25

Bharat

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2 Comments

Gabriel Takyie Over a year ago

but now when i write a date that doesn't exist, it gives me error

Gabriel Takyie Over a year ago

An exception of type 'System.InvalidOperationException' occurred in System.Data.dll but was not handled in user code Additional information: Invalid attempt to read when no data is present.

Ankit Jain · Accepted Answer · 2016-10-25 13:29:35Z

1

First, filter query with proper date format i.e. Parameter be in data format Second, while reading data from datareader, specify the proper column name.

answered Oct 25, 2016 at 13:29

Ankit Jain

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