Programm Error: Invalid Objectname System.Data.DataRowView

Question

4.00/5 (1 vote)

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Hallo i've tried many posibilities but i ain't getting it:
I have two comboboxes and a button. i wanna first choose from each combobox and dispaly the records in Form2 (datagridview)

C#

public partial class Form1 : Form
    {
       
private void button1_Click(object sender, EventArgs e)
        {
            //Connection string
            string C = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection con = new SqlConnection(C);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;

            //write a query
            Form2 f2 = new Form2();
            string qry = "";
            string qrynew = " select " + cbNr.SelectedItem  + " from " + cbTbl.SelectedItem + " where [DBN Zeichen] = 'AB' ";
            
            if (cbTbl.SelectedItem != null && cbEIU.SelectedItem != null)
            {
                    this.Hide();
                    f2.copyfun(qrynew);       
                    f2.show();
                }
                else
                {
                    MessageBox.Show ("ERROR First choose a tbl");
                }
            }
        }
    }

Form2:

C#

     public partial class Form2 : Form
    {
        public Standardbericht()
        {
            InitializeComponent();
        }

        DataTable dt;

        private void Standardbericht_Load(object sender, EventArgs e)
        {
            //lbTblname.Text = cbTbl.Text;
            string C = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection con = new SqlConnection(C);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;

        }
        // Get/ retrieve records from the previous page
        private void loadgrid(string qrynew)
        {
            string C = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection con = new SqlConnection(C);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = (qrynew);
            DataSet d = new DataSet();
            //dt = new DataTable();
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(d);
            dgvSbericht.DataSource = d;
            //dgvSbericht.DataSource = d.Tables[0];

        }

        public void copyfun(string qrynew)
        {
            loadgrid(qrynew);
        }
    }
}

My Query

SQL

string qrynew = "SELECT " + cbNr.SelectedItem  + " from " + cbTbl.SelectedItem + " where [DBN Zeichen] = 'AB'";

And that's what i get if i debug it on line (cmd.CommandText = (qrynew):

Quote:
select 16 from System.Data.DataRowView where [DBN Zeichen] = 'AB'

Posted 19-Nov-14 7:49am

mikybrain1

Updated 19-Nov-14 8:54am

v3

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2 solutions

Solution 1

cbTbl.SelectedItem is DataRowView, so you need to get the value as below

C#

cbTbl.SelectedItem.Row["ColumnName"].ToString()

and also cbNr.SelectedItem giving you value as 16 may be you want cbNr.SelectedItem.Text or cbNr.SelectedItem.Value depending on how you done the data binding.
any way this way of concatenating sql string is open for sql injection attacks. you better always try to use parameterized query

Posted 19-Nov-14 8:03am

DamithSL

Comments

mikybrain1 19-Nov-14 14:08pm

Thnx the problem is that i don't wanna choose the column name but rather from the FROM clause dynamically. Is it possible? Or how can i get the records in a different way?

DamithSL 19-Nov-14 14:11pm

yes, some cases you have to build sql query but make sure that all the inputs are safe. You better include the codes of how you bind two combo boxes.

mikybrain1 19-Nov-14 14:23pm

what do u please mean with "include the codes"? shd i post it for improvemennt?

DamithSL 19-Nov-14 14:26pm

update the question with relevant code

mikybrain1 19-Nov-14 14:59pm

I' ve updatet it. I 'trying to display certain columns of a dynamic table in a DB based on the selected items (also dynamic) to a second Form.
Would be glad if u can help

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mikybrain1 · Accepted Answer · 2014-11-21T02:34:00

With a lot of intensity i finally solved it. Bravo

C#

public partial class Form1 : Form
    {
       
private void button1_Click(object sender, EventArgs e)
        {
            //Connection string
            string C = ConfigurationManager.ConnectionStrings["DB"].ConnectionString;
            SqlConnection con = new SqlConnection(C);
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandText = ("sp");
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.Parameters.AddWithValue("@table_name", cbTbl.SelectedValue);

 
            //write a query
            Form2 f2 = new Form2();
            string qry = "";
            string qrynew = cmd.CommandText
            
            if (cbTbl.SelectedItem != null && cbNr.SelectedItem != null)
            {
                    this.Hide();
                    f2.copyfun(qrynew);       
                    f2.show();
                }
                else
                {
                    MessageBox.Show ("ERROR First choose a tbl");
                }
            }
        }
    }