在Datatable，DataView和DataGridView中不顯示重複的記錄



在Datatable，DataView和DataGridView中不顯示重複的記錄

其中，對於直接在查詢語句中使用distinct不作過多說明，主要從代碼層角度實現

方法一，在加載數據的時候，對於重複的數據，選擇不進行加載。
代碼如下：

<span style="font-size:14px;">OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Program\Database\employInfo.accdb");
            conn.Open();
            OleDbDataReader dr;
            OleDbCommand view = new OleDbCommand("SELECT * FROM Employ", conn);
            dataGridView1.Rows.Clear();
            dr = view.ExecuteReader();
            int ii = dataGridView1.Rows.Count;
            bool isexist = false;
            while (dr.Read())
            {
                if (dataGridView1.Rows.Count == 0)
                {
                    dataGridView1.Rows.Add(dr["EmployId"], dr["EmployName"], dr["EmployCompany"]);
                }
                else
                {
                    for (int i = 0; i < dataGridView1.Rows.Count; i++)
                    {
                        if (dataGridView1.Rows[i].Cells["EmployId"].Value.ToString() == dr["EmployId"].ToString()
                        && dataGridView1.Rows[i].Cells["EmployName"].Value.ToString() == dr["EmployName"].ToString()
                            && dataGridView1.Rows[i].Cells["EmployCompany"].Value.ToString() == dr["EmployCompany"].ToString())
                        {
                            isexist=true;
                            break;
                        }                        
                    }
                    if (!isexist)
                    {
                        dataGridView1.Rows.Add(dr["EmployId"], dr["EmployName"], dr["EmployCompany"]);                        
                    }
                    isexist = false;
                }
            }
            dr.Close();
            conn.Close();</span>

方法二.在現有的Datatable中去重，.net2.0提供了一個非常有效的方法DataView.ToTable 方法
具體代碼如下：

 OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Program\Database\employInfo.accdb");
            conn.Open();
            OleDbDataReader dr;
            OleDbCommand view = new OleDbCommand("SELECT * FROM Employ", conn);
            dataGridView1.Rows.Clear();
            dr = view.ExecuteReader();
            int ii = dataGridView1.Rows.Count;
            bool isexist = false;
            while (dr.Read())
            {
                dataGridView1.Rows.Add(dr["EmployId"], dr["EmployName"], dr["EmployCompany"]);
            }
            dr.Close();
            conn.Close();
            
            DataTable dt = new DataTable();
            OleDbDataAdapter da = new OleDbDataAdapter();
            da.SelectCommand = view;
            da.Fill(dt);
            DataTable dtnew = dt.DefaultView.ToTable(true);
            dataGridView2.DataSource = dtnew;//dtnew and dt both are DataTable

關於DataView.ToTable 方法可以參照如下鏈接：
http://msdn.microsoft.com/zh-cn/library/wec2b2e6(v=vs.110).aspx