Invalid attempt to read when no data is present

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1.00/5 (1 vote)

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C#

<blockquote class="quote"><div class="op">Quote:</div>          try
            {
                if (cn.State.ToString() != "Open")
                    cn.Open();
                cmd = new SqlCommand("select Antibiotic,RectionA,RectionB  from Culture", cn);
                dr = cmd.ExecuteReader();

                for (int i = 0; i < 5; i++)
                {
                    dataGridView5.Rows.Add(dr["Antibiotic"].ToString());
                    dataGridView5.Rows.Add(dr["RectionA"].ToString());
                    dataGridView5.Rows.Add(dr["RectionB"].ToString());
                }
                dr.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message + "eeee");
            }
            finally
            {
                cn.Close();
            }</blockquote>

What I have tried:

I want read data from sql server to my datagriedview 

but in datagriedview i have 3 columns

please help me

Posted 4-Dec-18 7:34am

waleed_akre

Updated 4-Dec-18 8:03am

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Comments

Richard MacCutchan 4-Dec-18 15:02pm

Always check the return value in dr to see if you actually received any data.

2 solutions

Solution 1

It appears that dr is null after the query. You need to perform a check dr.HasRows before going into the loop. You need to use foreach rather than a for in your loop rather than assuming the number of rows.

Posted 4-Dec-18 8:03am

User 9916080

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Karthik_Mahalingam · Accepted Answer · 2018-12-04T17:54:00

Try using sqldataadapter[^]

SqlCommand cmd = new SqlCommand("select Antibiotic,RectionA,RectionB  from Culture", con);
           SqlDataAdapter da = new SqlDataAdapter(cmd);
           DataTable dt = new DataTable();
           da.Fill(dt);
           for (int i = 0; i < dt.Rows.Count; i++)
           {
               if (i < 5) {
                   DataRow row = dt.Rows[i];
                   dataGridView5.Rows.Add(row["Antibiotic"].ToString(), row["RectionA"].ToString(), row["RectionB"].ToString());
               }
           }

This will display only the top 5 rows as per your code logic, if you want to load all the data to gridview, remove the IF condition