SQL查询填写backgroundworker后，数据表未显示信息 [英] Datatable not displaying information after SQL query fill in backgroundworker
问题描述
我正在用SQL查询中的数据填充DataTable.因为它可能很慢，所以我正在运行查询，并使用BackgroundWorker在DataTable上进行了一些计算.我知道后台线程已运行，因为在RunWorkerCompleted中，我设置了MessageBox来显示消息.但是，一旦完成，DataTable中将不会显示任何数据.
我知道这段代码有效，因为当我直接从按钮单击运行而不使用BackgroundWorker时，我会在DataTable中看到所有期望的数据. UI的更新和BackgroundWorker可能是问题所在，因为我知道您不能直接从另一个线程更新UI，但老实说我不知道.我的代码在下面.
DataTable tab1table = new DataTable();
public Form1()
{
InitializeComponent();
Instantiatesearch1Thread();
}
private void Instantiatesearch1Thread()
{
search1Thread.WorkerReportsProgress = true;
search1Thread.WorkerSupportsCancellation = true;
search1Thread.ProgressChanged += search1Thread_ProgressChanged;
search1Thread.DoWork += search1Thread_Dowrk;
search1Thread.RunWorkerCompleted += search1Thread_RunWorkerCompleted;
}
private void sbutton1_Click(object sender, EventArgs e)
{
search1Thread.RunWorkerAsync();
}
void search1Thread_Dowrk(object sender, DoWorkEventArgs e)
{
int percentprogress = 0;
percentprogress++;
Thread.Sleep(1000);
// Search1 button event handler
using (SqlConnection conn = new SqlConnection(connectionstring))
{
conn.Open();
using (SqlDataAdapter cmd = new SqlDataAdapter(comboBox1SQL, conn))
{
if (comboBox1.Text.Contains("ID"))
{
long para = long.Parse(search1.Text);
cmd.SelectCommand.Parameters.Add(new SqlParameter
{
ParameterName = "@combo1Par",
Value = para,
SqlDbType = SqlDbType.BigInt
});
}
else if (comboBox1.Text.Contains("Other Thing") || comboBox1.Text.Contains("Other Stuff"))
{
string para = search1.Text;
cmd.SelectCommand.Parameters.Add(new SqlParameter
{
ParameterName = "@combo1Par",
Value = "%" + para + "%",
SqlDbType = SqlDbType.NVarChar,
});
}
// Clear datatable if it contains any information and then fill it
// tab1datatable is a DataGridView
if (tab1table != null)
tab1table.Clear();
cmd.Fill(tab1table);
tab1datatable.DataSource = tab1table;
// A bunch of long calculations
}
}
}
void search1Thread_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
search1Progress.Value = e.ProgressPercentage;
}
void search1Thread_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
MessageBox.Show("All Done!");
}
对于BackgroundWorker，您必须稍作更改:
只需更新其中的DataTable，然后在您的search1Thread_RunWorkerCompleted上调用数据源更新过程即可，而不是更新BackgroundWorker的search1Thread_Dowrk中DataGridView的DataSource.
从此更改您的代码:
void search1Thread_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
MessageBox.Show("All Done!");
}
收件人:
void search1Thread_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
tab1datatable.DataSource = tab1table;
tab1datatable.Refresh();
MessageBox.Show("All Done!");
}
I am filling a DataTable with the data from a SQL query. As it can be quite slow, I am running the query and doing some computations on the DataTable using BackgroundWorker. I know the background thread has run because in RunWorkerCompleted I have set a MessageBox to display a message. Once complete, however, there is no data displayed in the DataTable.
I know this code works, because when I run directly from the button click and not using BackgroundWorker, I see all the expected data in the DataTable. The issue is likely something with how the UI updates and the BackgroundWorker, as I know you can't update the UI directly from another thread, but I honestly don't know. My code is below.
DataTable tab1table = new DataTable();
public Form1()
{
InitializeComponent();
Instantiatesearch1Thread();
}
private void Instantiatesearch1Thread()
{
search1Thread.WorkerReportsProgress = true;
search1Thread.WorkerSupportsCancellation = true;
search1Thread.ProgressChanged += search1Thread_ProgressChanged;
search1Thread.DoWork += search1Thread_Dowrk;
search1Thread.RunWorkerCompleted += search1Thread_RunWorkerCompleted;
}
private void sbutton1_Click(object sender, EventArgs e)
{
search1Thread.RunWorkerAsync();
}
void search1Thread_Dowrk(object sender, DoWorkEventArgs e)
{
int percentprogress = 0;
percentprogress++;
Thread.Sleep(1000);
// Search1 button event handler
using (SqlConnection conn = new SqlConnection(connectionstring))
{
conn.Open();
using (SqlDataAdapter cmd = new SqlDataAdapter(comboBox1SQL, conn))
{
if (comboBox1.Text.Contains("ID"))
{
long para = long.Parse(search1.Text);
cmd.SelectCommand.Parameters.Add(new SqlParameter
{
ParameterName = "@combo1Par",
Value = para,
SqlDbType = SqlDbType.BigInt
});
}
else if (comboBox1.Text.Contains("Other Thing") || comboBox1.Text.Contains("Other Stuff"))
{
string para = search1.Text;
cmd.SelectCommand.Parameters.Add(new SqlParameter
{
ParameterName = "@combo1Par",
Value = "%" + para + "%",
SqlDbType = SqlDbType.NVarChar,
});
}
// Clear datatable if it contains any information and then fill it
// tab1datatable is a DataGridView
if (tab1table != null)
tab1table.Clear();
cmd.Fill(tab1table);
tab1datatable.DataSource = tab1table;
// A bunch of long calculations
}
}
}
void search1Thread_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
search1Progress.Value = e.ProgressPercentage;
}
void search1Thread_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
MessageBox.Show("All Done!");
}
For the BackgroundWorker you have to change your process a bit:
Instead of updating the DataSource of the DataGridView in the search1Thread_Dowrk of BackgroundWorker just update the DataTable in it and then on your search1Thread_RunWorkerCompleted call the DataSource updation process.
Change you code from this:
void search1Thread_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
MessageBox.Show("All Done!");
}
To:
void search1Thread_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
tab1datatable.DataSource = tab1table;
tab1datatable.Refresh();
MessageBox.Show("All Done!");
}
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