How to link data from a textbox to a Datagridview in different windows in C #

You are missing information for your question, but if you need to access form 1 from 2, you must:

 Form1 form_Principal = new Form1();
 ((TextBox)form_Principal.Controls["TextBox1"]).Text = "Texto";

And to fill your datagrid:

   DataTable dt = new DataTable();
   MySqlCommand comando = new MySqlCommand("select * from tabla where id='"+textBox11.Text+"'", conexion);
   MySqlDataAdapter sda = new MySqlDataAdapter(comando);
   sda.Fill(dt);
   dataGridView1.DataSource = dt;

This code can adapt it to your needs

You must place for each column of your datagrig and the field of your table.

Greetings ..

  Try

            Dim ivNumerCredito = DataGridView1.Rows(e.RowIndex).Cells(1).Value()
            Dim oConn As SqlConnection
            oConn = New SqlConnection("Server=192.168.105.150\SQL2012;   database=DBProAuxQP;      user id=sa;               password=DBServ@14;")
            If oConn.State = 1 Then oConn.Close()
            oConn.Open()
            Dim table As New DataTable
            Dim Adp As New SqlDataAdapter()
            Adp.SelectCommand = New SqlCommand() ' Creando una Instancia de SqlCommand
            Adp.SelectCommand.Connection = oConn 'Conexión
            Adp.SelectCommand.CommandText = "PE_Cre_Consulta_Cargo"
            Adp.SelectCommand.CommandTimeout = 90000000
            Adp.SelectCommand.CommandType = CommandType.StoredProcedure
            Adp.SelectCommand.Parameters.Add("@opt", SqlDbType.Int, 4)
            Adp.SelectCommand.Parameters("@opt").Value = 3
            Adp.SelectCommand.Parameters.Add("@NomServer", SqlDbType.VarChar, 50)
            Adp.SelectCommand.Parameters("@NomServer").Value = CboServidor.Text
            Adp.SelectCommand.Parameters.Add("@FechaCarga", SqlDbType.Date)
            Adp.SelectCommand.Parameters("@FechaCarga").Value = "2013-11-25"
            Adp.SelectCommand.Parameters.Add("@Buscar", SqlDbType.VarChar, 15)
            Adp.SelectCommand.Parameters("@Buscar").Value = ivNumerCredito
            Adp.SelectCommand.Parameters.Add("@NCuota", SqlDbType.Int)
            Adp.SelectCommand.Parameters("@NCuota").Value = 0

            Adp.Fill(table)

            Me.Close()


            Dim frm As New Form3
            frm.Show()
            frm.TxtNroCredito.Text = ivNumerCredito
            frm.TxtCliente.Text = table.Rows(0)("Nombres")
            If table.Rows.Count > 0 Then
                frm.DtgCargos.Visible = True
                frm.DtgCargos.Rows.Clear()
                For Each Frow As DataRow In table.Rows
                    frm.DtgCargos.Rows.Add(Frow.Item("IdcuotaCredito"), Frow.Item("Numero"), Frow.Item("FVto"), Frow.Item("Otros"), Frow.Item("Estado"))
                Next
            End If

            table.Dispose()

        Catch ex As Exception
            MsgBox(Err.Description, MsgBoxStyle.Critical, "..:: Aviso del Sistema ::..")
            Exit Try
        End Try

    End Sub