System.InvalidOperationExcepti...

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SQL-Server-2005

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Hi,

i am getting this error

System.InvalidOperationException: Invalid attempt to read when no data is present.

i used this code:

SqlDataReader dr = command.ExecuteReader();

while (dr.Read())
{
if (dr["emailId"].ToString() !=txtenrEmail.Text)
{
Label1.Text = "Emailid already exists. Use another EmailId";
}
else
{
Label1.Text = "User details Inserted successfully";
}
}

String strQuery = "";
SqlConnection mySqlConnection = new SqlConnection(str);

strQuery += "update PersonalDetails set EnrolmentNo= ('CD' + ' " + dr["userid"].ToString() + " ') where userid = ' " + Convert.ToInt32(dr["userid"]) + " ' ";
SqlCommand com = new SqlCommand(strQuery, mySqlConnection);
mySqlConnection.Open();
com.ExecuteNonQuery();
mySqlConnection.Close();

con.Close();

please help me..............

Posted 24-Mar-13 19:12pm

suma2212

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KM Perumal 25-Mar-13 3:10am

Please show ur whole event coding

1 solution

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Pallavi Waikar · Answer 1 · 2013-03-24T20:29:00

Solution 1

u have to check dr.HasRows in if, before update query

C#

if(dr.HasRows)
{
String strQuery = "";
SqlConnection mySqlConnection = new SqlConnection(str);
 
strQuery += "update PersonalDetails set EnrolmentNo= ('CD' + ' " + dr["userid"].ToString() + " ') where userid = ' " + Convert.ToInt32(dr["userid"]) + " ' ";
SqlCommand com = new SqlCommand(strQuery, mySqlConnection);
mySqlConnection.Open();
com.ExecuteNonQuery();
mySqlConnection.Close();
 
con.Close();
}

Posted 24-Mar-13 20:29pm

Pallavi Waikar

Comments

suma2212 25-Mar-13 2:38am

Hi i used if(dr.HasRows)
{
}
but i got this error

Object cannot be cast from DBNull to other types.
please help me.......

Pallavi Waikar 25-Mar-13 2:46am

i think u r facing this problem becouse u already get all values of dr using while and then ur trying to update...best way store this values in two variable in while and use them for update..i.e string userid =dr["userid"].ToString() ; when get match in while

suma2212 25-Mar-13 3:03am

ya i got it.thanx for ur help......

is this code correct?

while (dr.Read())
{
if (dr["emailId"].ToString() !=txtenrEmail.Text)
{
Label1.Text = "User details Inserted successfully";
}
else
{
Label1.Text = "Emailid already exists. Use another EmailId";

}
}

if that emailid is already exists i got this message
Label1.Text = "Emailid already exists. Use another EmailId";
and emailid not exists also i am getting same message..

please help me..

Pallavi Waikar 25-Mar-13 3:33am

best way search in select query cmd= "select * from urTablename where emailId= '"+txtenrEmail.Text+"'"
and use if instead of while
dr=cmd..ExecuteReader();
if (dr.Read())
{
if (dr["emailId"].ToString() !=txtenrEmail.Text)
{
string uid=dr["userid"].ToString();
string emailid=dr["emailId"].ToString();
Label1.Text = "User details Inserted successfully";
}
else
{
Label1.Text = "Emailid already exists. Use another EmailId";
}
}

KM Perumal 25-Mar-13 3:11am

Try sql Adapter

suma2212 25-Mar-13 3:16am

i want to read 2 values userid and emailid. so i used sql reader.... please check above code...

suma2212 25-Mar-13 3:48am

sorry for the trouble i am using this

SqlDataReader dr = command.ExecuteReader();

while (dr.Read())
{
if (dr["emailId"].ToString() !=txtenrEmail.Text)
{
Label1.Text = "Emailid already exists. Use another EmailId";
}
else
{
Label1.Text = "User details Inserted successfully";
}
}

String strQuery = "";
SqlConnection mySqlConnection = new SqlConnection(str);

strQuery += "update PersonalDetails set EnrolmentNo= ('CD' + ' " + dr["userid"].ToString() + " ') where userid = ' " + Convert.ToInt32(dr["userid"]) + " ' ";
SqlCommand com = new SqlCommand(strQuery, mySqlConnection);
mySqlConnection.Open();
com.ExecuteNonQuery();
mySqlConnection.Close();

con.Close();

please check it once......