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POBeginInvoke() occasionally breaks (System.InvalidOperationException) with Invalid attempt to call Read when reader is closed
 

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    <p>In following code snippet, <code>AddRow()</code> is called from a non-UI thread:</p> <pre><code> public partial class Form1 : Form { public delegate void InvokeDelegate(); ... SqlConnection mSqlConnection = new SqlConnection("Data Source=" + Environment.MachineName + "\\SQLEXPRESS; Initial Catalog=orderDB; Integrated Security=TRUE; MultipleActiveResultSets=True;"); DataSet mDataSet = new DataSet(); SqlDataAdapter mSqlDataAdapter = new SqlDataAdapter(); ... private void UpdateGridView() { if (mSqlConnection.State == ConnectionState.Closed) mSqlConnection.Open(); mSqlDataAdapter.SelectCommand = new SqlCommand("SELECT * FROM customerTable", mSqlConnection); mDataSet.Clear(); mSqlDataAdapter.Fill(mDataSet); dataGridView1.DataSource = mDataSet.Tables[0]; if (mSqlConnection.State == ConnectionState.Open) mSqlConnection.Close(); } public void AddRow(int field1, int field2, int field3) { mSqlDataAdapter.InsertCommand = new SqlCommand("INSERT INTO customerTable VALUES(@field1, @field2, @field3)", mSqlConnection); mSqlDataAdapter.InsertCommand.Parameters.Add("@field1", SqlDbType.Int).Value = field1; mSqlDataAdapter.InsertCommand.Parameters.Add("@field2", SqlDbType.Int).Value = field2; mSqlDataAdapter.InsertCommand.Parameters.Add("@field3", SqlDbType.Int).Value = field3; mSqlConnection.Open(); mSqlDataAdapter.InsertCommand.ExecuteNonQuery(); dataGridView1.BeginInvoke(new InvokeDelegate(UpdateGridView)); // UpdateGridView() won't work from a non-UI thread mSqlConnection.Close(); } } </code></pre> <p>Before having to call <code>AddRow()</code> from a non-UI thread, I had <code>UpdateGridView()</code> being called directly and it worked flawlessly. But now <code>AddRow()</code> is no longer guaranteed to be called from a UI thread and so I replaced the direct call with <code>dataGridView1.BeginInvoke()</code>.</p> <p>As soon as I did that, my form-based application started throwing a <code>System.InvalidOperationException</code> every several <code>AddRow()</code> calls, breaking on the <code>mSqlDataAdapter.Fill(mDataSet);</code> statement (<strong>!</strong>) with the following message:</p> <blockquote> <p>Invalid attempt to call Read when reader is closed</p> </blockquote> <p>My question is why?</p> <ol> <li>What reader? the DataAdapter's? The SqlConnection's? The DataGridView's data source?</li> <li>I am taking care of surrounding <code>BeginInvoke()</code> with mSqlConnection's <em>Open()</em> and <em>Close()</em> and I even open mSqlConnection (again!) if it isn't open, so how come I'm receiving this "closed" error?</li> <li>What is the correct way to solve this problem? (i.e. updating DataGridView from a non-UI thread)</li> </ol>
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