如何在一种形式（c＃）中使用2个DataGridViews？

Question

我想在这种形式中使用两个DataGridViews，它将从一个数据库中的两个不同的表中接收它们的信息。但是当我运行程序时，两个DataGridViews只显示第二个表信息。

private void Ring_Load(object sender, EventArgs e)
{
    showdata();
    showmedal();  
}

void showdata()
{
    SqlConnection con = new SqlConnection(conn);
    SqlCommand cmd = new SqlCommand("SELECT Number,Weight,Ring_Id FROM Ring", con);
    da.SelectCommand = cmd;
    dt.Clear();
    da.Fill(dt);
    dataGridView1.DataSource = dt;
    dataGridView1.Columns[3].Visible = false;

}

void showmedal()
{
    SqlConnection con = new SqlConnection(conn);
    SqlCommand cmd = new SqlCommand("SELECT Number,Weight,Ring_Id FROM medal", con);
    da.SelectCommand = cmd;
    dt.Clear();
    da.Fill(dt);
    dataGridView2.DataSource = dt;
}

Answer 1

private void Ring_Load(object sender, EventArgs e)
{
    showdata();
    showmedal();  
}

void showdata()
{
    SqlConnection con = new SqlConnection(conn);
    SqlCommand cmd = new SqlCommand("SELECT Number,Weight,Ring_Id FROM Ring", con);
    da.SelectCommand = cmd;
    using(DataTable dt = new DataTable())
    {
        da.Fill(dt);
        dataGridView1.DataSource = dt;
        dataGridView1.DataBind();
        dataGridView1.Columns[3].Visible = false;
    }
}
void showmedal()
{
    SqlConnection con = new SqlConnection(conn);
    SqlCommand cmd = new SqlCommand("SELECT Number,Weight,Ring_Id FROM medal", con);
    da.SelectCommand = cmd;
    using(DataTable dt = new DataTable())
    {
        da.Fill(dt);
        dataGridView2.DataSource = dt;
        dataGridView2.DataBind();
    }
}

Answer 2

试试这个

private void Ring_Load(object sender, EventArgs e)
{
    showdata();
    showmedal();  
}

void showdata()
{
    SqlConnection con = new SqlConnection(conn);
    SqlCommand cmd = new SqlCommand("SELECT Number,Weight,Ring_Id FROM Ring", con);
    da.SelectCommand = cmd;
    dt.Clear();
    da.Fill(dt);
    dataGridView1.DataSource = dt;
    dataGridView1.Columns[3].Visible = false;

}

void showmedal()
{
    SqlConnection con = new SqlConnection(conn);
    SqlCommand cmd = new SqlCommand("SELECT Number,Weight,Ring_Id FROM medal", con);
    da.SelectCommand = cmd;
    dt.Clear();
    dt = new DataTable();
    da.Fill(dt);
    dataGridView2.DataSource = dt;
}

Answer 3

你好像在重用da和dt。重用da没问题，但重用dt是。将dt分配给DataGridView.DataSource时，不会复制数据！所以最后，两个DataGridViews都将使用相同的DataTable对象，该对象保存第二个表（medal）中的数据。

你可以试试这个：

private void Ring_Load(object sender, EventArgs e)
{
    showdata();
    showmedal();  
}

void showdata()
{
    SqlConnection con = new SqlConnection(conn);
    SqlCommand cmd = new SqlCommand("SELECT Number,Weight,Ring_Id FROM Ring", con);
    da.SelectCommand = cmd;
    DataTable dt1 = new DataTable();
    da.Fill(dt1);
    dataGridView1.DataSource = dt1;
    dataGridView1.Columns[3].Visible = false;

}
void showmedal()
{
    SqlConnection con = new SqlConnection(conn);
    SqlCommand cmd = new SqlCommand("SELECT Number,Weight,Ring_Id FROM medal", con);
    da.SelectCommand = cmd;
    DataTable dt2 = new DataTable();
    da.Fill(dt2);
    dataGridView2.DataSource = dt2;
}

编辑：为了清楚起见，重命名了本地DataTable变量。