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http://www.connectionstrings.com

using System.Data.SqlClient;

SqlConnection con;

SqlCommand cmd;

private void Select0()

        {

listBox1.Items.Clear();

string s1 = @"SELECT * FROM TABLEA WHERE f1=" + textBox1.Text;

cmd = new SqlCommand(s1, con);

SqlDataReader rd = cmd.ExecuteReader();

if (rd.HasRows)

            {

while (rd.Read())

listBox1.Items.Add(rd["f1"] + "   " + rd["f2"]);

            }

rd.Close();

        }

private void Select1()

        {

listBox1.Items.Clear();

string s1 = @"SELECT * FROM TABLEA WHERE f1 = @s2";

cmd = new SqlCommand(s1, con);

cmd.Parameters.AddWithValue("@s2", textBox1.Text);

SqlDataReader rd = cmd.ExecuteReader();

if (rd.HasRows)

            {

while (rd.Read())

listBox1.Items.Add(rd["f1"] + "   " + rd["f2"]);

            }

rd.Close();

        }

private void Connect()

        {

con = new SqlConnection(@"Data Source=B325\SQL2012EXPRESS;Initial Catalog=test2;Integrated Security=True");         

con = new SqlConnection(@"Server=.\SQLExpress;AttachDbFilename=C:\MyFolder\MyDataFile.mdf;Database=dbname;Trusted_Connection=Yes");

con = new SqlConnection(@"Data Source=B325\SQL2012EXPRESS;Initial Catalog=test;User ID=krokodyl;Password=abc");

con.Open();

            button2.Text = con.State.ToString();

        }

private void Insert()

        {

// string s1 = @"INSERT INTO TABLEB (g1,g2) VALUES (11,'abc')";

string s1 = @"INSERT INTO TABLEB (g1,g2) VALUES ("+textBox2.Text+",'"+textBox3.Text+"')";

cmd = new SqlCommand(s1, con);

cmd.ExecuteNonQuery();

        }

private void Select2()

        {

listBox1.Items.Clear();

string s1 = @"SELECT * FROM TABLEA; SELECT * FROM TABLEB";

cmd = new SqlCommand(s1, con);

SqlDataReader rd = cmd.ExecuteReader();

do

            {

while (rd.Read())

                {

string s3 = "";

for (int i = 0; i < rd.FieldCount; i++)

                    {

                        s3 += rd[i] + "    ";

                    }

listBox1.Items.Add(s3);

                }

            }

while (rd.NextResult());

rd.Close();

        }

private void Update()

        {

string s1 = @"Update TableA set f2='YYYYYYYY' Where f1<3";

cmd = new SqlCommand(s1, con);

int nr = cmd.ExecuteNonQuery();

            textBox1.Text = nr.ToString();

        }

private void Delete()

        {

string s1 = @"Delete from TableA Where f1<3";

cmd = new SqlCommand(s1, con);

int nr = cmd.ExecuteNonQuery();

            textBox1.Text = nr.ToString();

}

/*

         *

         *   CHAR(1000)

         *   NCHAR(1000)

         *   VARCHAR(1000)

         *   NVARCHAR(1000)

         *  

         */