Check return of sql command in c#

Question

I want to check if my query returns any value or not and write the remaining logic accordingly.

SqlCommand myCommand = new SqlCommand("Select * from phc.userbase where [user]='@Username' and [password]='@password'", myConnection);

I want to know this command returns null or not. I tried

myReader = myCommand.ExecuteReader();
bool rd = myReader.Read();

if rd==false

but I can't get it working. Any ideas?

Here are my parameters:

SqlParameter myParam = new SqlParameter("@Username", SqlDbType.VarChar, 25);
myParam.Value = usr;

SqlParameter myParam2 = new SqlParameter("@password", SqlDbType.VarChar, 25);
myParam2.Value = pass;

So... you're storing passwords as plain text in the database? That is not good. Also, it isn't clear if you are parameterizing that correctly - the parameters should probably not be in quotes. — Marc Gravell
– Marc Gravell, Commented Mar 15, 2012 at 8:10
@MarcGravell this is just a dummy demo.I plan to use MD5 encryption later. — deception1
– deception1, Commented Mar 15, 2012 at 8:12
To clarify: at the moment you are searching for a user called '@Username' with a password of '@Password' - which is very different to checking whether they have a username the same as the value of the parameter @Username. I bet that query always returns zero rows, right? — Marc Gravell
– Marc Gravell, Commented Mar 15, 2012 at 8:14
yes; as I've already mentioned twice: take the quotes away. The quotes are wrong here. Should be [user] = @Username and [password] = @password - look - no quotes! — Marc Gravell
– Marc Gravell, Commented Mar 15, 2012 at 8:24

Marc Gravell · Accepted Answer · 2012-03-15 08:31:01Z

2

It depends what you mean by null here; do you mean "no rows" ? If so:

using(var myReader = myCommand.ExecuteReader()) {
    if(myReader.Read()) {
      // at least 1 row; can now check columns
    } else {
      // no rows
    }
}

To be honest, though, you could probably change that to SELECT 1 ... and use ExecuteScalar - much less bother.

In this case, though, it is probably easier to just SELECT 1 ...rest of query... and use:

object value = myCommand.ExecuteScalar();
if(value != null) { ... got a row ...}

edited Mar 15, 2012 at 8:31

answered Mar 15, 2012 at 8:08

Marc Gravell

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1 Comment

deception1 Over a year ago

Can you point me in the right direction with the execute scalar

Shai · Accepted Answer · 2012-03-15 08:08:16Z

2

use SqlDataReader.HasRows()

if (myReader.HasRows())
{
    // Do something
}

answered Mar 15, 2012 at 8:08

Shai

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2 Comments

deception1 Over a year ago

I just want to know if my query returns a value or not.forgive me if i'm wrong but,wouldn't this check for values inside a table?

Marc Gravell Over a year ago

@deception1 your query has a filter; it will only HasRows() if your query finds a match

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