在Datatable，DataView和DataGridView中不显示重复的记录
其中，对于直接在查询语句中使用distinct不作过多说明，主要从代码层角度实现
方法一，在加载数据的时候，对于重复的数据，选择不进行加载。
代码如下：
<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.在现有的Datatable中去重，.net2.0提供了一个非常有效的方法DataView.ToTable 方法
具体代码如下：
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 关于DataView.ToTable 方法可以参照如下链接：
http://msdn.microsoft.com/zh-cn/library/wec2b2e6(v=vs.110).aspx
