private void button1_Click(object sender, EventArgs e)
{
string name;
name = textBox5.Text;
SqlConnection con10 = new SqlConnection("con strn");
SqlCommand cmd10 = new SqlCommand("select * from sumant where username=@name");
cmd10.Parameters.AddWithValue("@name",name);
cmd10.Connection = con10;
cmd10.Connection.Open();//line 7
SqlDataReader dr = cmd10.ExecuteReader();
}
if ( textBox2.Text == dr[2].ToString())
{
//do something;
}
When I debug until line 7, it is OK, but after that dr throws an exception:
Invalid attempt to read when no data is present.
I don't understand why I'm getting that exception, since I do have data in the table with username=sumant.
Please tell me whether the 'if' statement is correct or not. And how do I fix the error?
This question is related to
c#
ado.net
sqldatareader
You have to call DataReader.Read to fetch the result:
SqlDataReader dr = cmd10.ExecuteReader();
if (dr.Read())
{
// read data for first record here
}
DataReader.Read() returns a bool indicating if there are more blocks of data to read, so if you have more than 1 result, you can do:
while (dr.Read())
{
// read data for each record here
}
I was having 2 values which could contain null values.
while(dr.Read())
{
Id = dr["Id"] as int? ?? default(int?);
Alt = dr["Alt"].ToString() as string ?? default(string);
Name = dr["Name"].ToString()
}
resolved the issue
I used the code below and it worked for me.
String email="";
SqlDataReader reader=cmd.ExecuteReader();
if(reader.Read()){
email=reader["Email"].ToString();
}
String To=email;
You have to call dr.Read() before attempting to read any data. That method will return false if there is nothing to read.
I just had this error, I was calling dr.NextResult() instead of dr.Read().
I would check to see if the SqlDataReader has rows returned first:
SqlDataReader dr = cmd10.ExecuteReader();
if (dr.HasRows)
{
...
}
Source: Stackoverflow.com