Sql
using System.Data.SqlClient;

public void GetYourDbDatasToArray() {
        List<object[]> temp = new List<object[]>();
        using(SqlConnection con = new SqlConnection("YourConnectionString")) {
            using(SqlCommand cmd = new SqlCommand("YourSelectString", con)) {
                con.Open();
                SqlDataReader reader = cmd.ExecuteReader();
                while(reader.Read()) {
                    temp.Add(new object[] { reader.GetValue(0), reader.GetValue(1), reader.GetValue(2) });//数据库的表有 n 列，就写 n 个 GetValue(i)，其中 0<= i < n
                }
                //迁移到你的二维数组
                object[][] YourTargetArray = new object[temp.Count][];//你的二维数组，以实际为主
                temp.CopyTo(YourTargetArray);
            }
        }
    }