Error:System.IndexOutOfRangeException

Question

I need your help, When I type something in the text box, it sends me the following error: "System.IndexOutOfRangeException" and Additional Information: "B.Nombre" . I don't know what it could be, I'm looking for the error even try with parameters and nothing. Thanks!

var strcn = System.Configuration.ConfigurationManager.ConnectionStrings["ConexionDB"].ToString();

using (SqlConnection con = new SqlConnection(strcn))
{
    con.Open();
    string commandString = @"SELECT  
           B.Nombre,G.Nombre,D.Nombre,B.Precio,G.Precio,D.Precio,
           B.Gramos,G.Gramos,D.Gramos,B.Tabletas,G.Tabletas,D.Tabletas
       FROM TblBenavides B INNER JOIN TblGuadalajara G ON B.Nombre = G.Nombre 
                           INNER JOIN TblDelAhorro D ON G.Nombre = D.Nombre 
       WHERE B.Nombre='" + TxtMedicamento.Text + "'" +
             "AND G.Nombre='" + TxtMedicamento.Text + 
             "' AND D.Nombre='" + TxtMedicamento.Text + "'";
    SqlCommand cmd = new SqlCommand(commandString, con);
    SqlDataReader myReader = cmd.ExecuteReader();
    if (myReader.Read())
    {
        label3.Text = myReader["B.Nombre"].ToString();
        label4.Text = myReader["G.Nombre"].ToString();
        label5.Text = myReader["D.Nombre"].ToString();
        this.label8.Text = myReader["B.Precio"].ToString();
        this.TxtGprecio.Text = myReader["G.Precio"].ToString();
        this.TxtDprecio.Text = myReader["D.Precio"].ToString();
        this.label6.Text = myReader["B.Gramos"].ToString();
        this.TxtGgramos.Text = myReader["G.Gramos"].ToString();
        this.TxtDgramos.Text = myReader["D.Gramos"].ToString();
        this.label7.Text = myReader["B.Tabletas"].ToString();
        this.TxtGtabletas.Text = myReader["G.Tabletas"].ToString();
        this.TxtDtabletas.Text = myReader["D.Tabletas"].ToString();
    }
}

Answer 1

B.Nombre,G.Nombre,D.Nombre all have the same column name because you don't specify aliases for them. The B,G,D prefixes are just the alias for the table-names but they are not part of the column-name. So you can't use myReader["B.Nombre"](for example) because that column doesn't exist(that's the reason for the exception).

Instead use column aliases for those columns or the int-indexer with the index of the column.

SELECT B.Nombre As B_Nombre,G.Nombre As G_Nombre, D.Nombre As D_Nombre
...

and then you can use these names, f.e.:

 label3.Text = myReader["B_Nombre"].ToString();

You can also use the the int-indexer:

 label3.Text = myReader[0].ToString(); // first column in the select

---

Instead of concatenating strings to build your sql query you should use parameterized queries, f.e. to avoid sql-injection.

Answer 2

You need to alias your column names.
So your query should be something like this for example:

var strcn = System.Configuration.ConfigurationManager.ConnectionStrings["ConexionDB"].ToString();

using (SqlConnection con = new SqlConnection(strcn))
{
    con.Open();
    string commandString = @"SELECT  
           B.Nombre as BNombre,G.Nombre as GNombre,D.Nombre as DNombre,B.Precio as BPrecio ,G.Precio as GPrecio,D.Precio as DPrecio,
           B.Gramos as BGramos,G.Gramos as GGramos,D.Gramos as DGramos,B.Tabletas as BTabletas,G.Tabletas as GTabletas,D.Tabletas as DTabletas
       FROM TblBenavides B INNER JOIN TblGuadalajara G ON B.Nombre = G.Nombre 
                           INNER JOIN TblDelAhorro D ON G.Nombre = D.Nombre 
       WHERE B.Nombre='" + TxtMedicamento.Text + "'" +
             "AND G.Nombre='" + TxtMedicamento.Text + 
             "' AND D.Nombre='" + TxtMedicamento.Text + "'";
    SqlCommand cmd = new SqlCommand(commandString, con);
    SqlDataReader myReader = cmd.ExecuteReader();
    if (myReader.Read())
    {
        label3.Text = myReader["BNombre"].ToString();
        label4.Text = myReader["GNombre"].ToString();
        label5.Text = myReader["DNombre"].ToString();
        this.label8.Text = myReader["BPrecio"].ToString();
        this.TxtGprecio.Text = myReader["GPrecio"].ToString();
        this.TxtDprecio.Text = myReader["DPrecio"].ToString();
        this.label6.Text = myReader["BGramos"].ToString();
        this.TxtGgramos.Text = myReader["GGramos"].ToString();
        this.TxtDgramos.Text = myReader["DGramos"].ToString();
        this.label7.Text = myReader["BTabletas"].ToString();
        this.TxtGtabletas.Text = myReader["GTabletas"].ToString();
        this.TxtDtabletas.Text = myReader["DTabletas"].ToString();
    }
}