从SQL Server表读取行

Question

This code only read ID 1 and I need to read all table. How can I go about this?

using (SqlConnection sqlConnection = new SqlConnection())
{
    sqlConnection.ConnectionString = "Data Source=TOMMY-PC\\SQLEXPRESS; Initial Catalog=Test; Integrated Security=True;";
    sqlConnection.Open();
    SqlCommand sqlCommand = new SqlCommand("SELECT * FROM dbo.Users");
    sqlCommand.Connection = sqlConnection;

    SqlDataAdapter adapter = new SqlDataAdapter();
    DataTable table = new DataTable();
    adapter.SelectCommand = sqlCommand;
    adapter.Fill(table);

    if ((string)table.Rows[0]["Name"] == textBox2.Text)
    {
        MessageBox.Show("Founded");
    }
}

Answer 1

To answer your direct question: you need to do a foreach loop, like this:

foreach (var row in table.Rows.Cast<DataRow>())
{
    var name = row["Name"];
    //Continue here
}

To explain the use of the Cast method:

The table.Rows which is of type DataRowCollection implements the older IEnumerable interface which enumerates over the rows but give us the rows as objects of type object not DataRow . We cast them to DataRow by using the Cast method.

Answer 2

If you are trying to find if a user with a specific name exists or not, then you don't need to read the whole table, but you could write a query that discovers if users with that name exist or not

using (SqlConnection sqlConnection = new SqlConnection())
using (SqlCommand sqlCommand = new SqlCommand())
{
    sqlConnection.ConnectionString = "....."";
    sqlCommand.Connection = sqlConnection;
    sqlCommand.CommandText = @"SELECT COUNT(*) FROM dbo.Users 
                        WHERE Name = @name";
    sqlConnection.Open();
    sqlCommand.Parameters.Add("@name", SqlDbType.NVarChar).Value = textBox2.Text;
    int result = Convert.ToInt32(sqlCommand.ExecuteNonQuery());
    if(result > 0) 
        MessageBox.Show("Founded " + result + " user/s");
    else
        MessageBox.Show("No user found with that name");
}