Passing Data from a Textbox into a SQL where Clause

string query = string.Format("SELECT data from Table Where UserName = '{0}'", TextBox1.Text);

string userName = txtUserName.Text;

SqlCommand cm = new SqlCommand("", YourConnection)
cm.CommandText = "Select FROM YourTable WHERE Name=@UserName"
cm.Parameters.Add("@UserName", SqlDbType.VarChar).Value = userName; 

SqlDataReader reader = cm.ExecuteReader();
if (reader.Read())
{
    // Whatever...
}

 string Value = TextBox.Text;
SqlConnection Con = new SqlConnection("Your Connection string");
Con.Open();
 SqlCommand Cmd = new SqlCommand("Select * from TableName where UserName = @Value"),Con);
 Cmd.Parameters.addwithvalue("@Value",Value);
 SqlDataAdatpter dt = new SqlDataAdapter(Cmd);
 DataSet ds = new DataSet();
 dt.fill(ds);
Con.Close();

SqlCommand command = new SqlCommand("SELECT Field1, Field2, Field3 FROM YourTable WHERE Field4 = @UserName;", connection);

command.Parameters.Add("@UserName", SqlDbType.String).Value = txtUserName.Text;

command.ExecuteNonQuery();

...
...
...