Search from one database using the values of another database

I tried constructing query but its giving me error

Here is my code for that
String strsql = "select * from customer where custID = " + TempCustID; //connecting database

DataTable customer = new Datable();
da1.Fill(Customer); // here I am getting error "no value given for one or more required parameters"
Datagridview1.data source = Customer;

I have two database In database1 I am having table1 (custid,productid,customername )
Database2 : table2 (productname,productid, pice, mfg)

I want to display all the products purchased by particular custid


Here is my code :
C#

using System.Data.SqlClient;

// .....

string queryString = "Select custID from Table1 where custId ="+ textbox1.text;
String TempCustID;

using (SqlConnection connection = new SqlConnection(connectionString))
{
SqlCommand command = new SqlCommand(queryString, connection);
connection.Open();
SqlDataReader reader = command.ExecuteReader();

while (reader.Read())
{
if (!reader.IsDBNull(0))
{
TempCustID = reader[0].ToString();

String stringprovider = "@database connection string ";
Sqlconnection con2 = new sqlconnection(stringprovider);
Con2.open();
Cmd2.connection=con2;
Cmd2.commandType = new commandType.text;
Cmd2.commandText = "select * from Table2 where Productid = @productid";
Cmd2.parameters.addwithvalue("@productid",TempCustID);
}
}
reader.Close();
Dataset Ds = new dataset();
Oledbdataadaptaer da1 = new oledbdataadapter(cmd2);
Datatable Table2 = new Data table();
Da1.fill(table2);
Datagridview2.source = table2;


}


In this I am getting only the first product details of that customer its not displaying all the products at a time.
Please suggest.

Its reading all the values but not displaying .. Even after using execute reader I am getting the same output only last value is getting displayed