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POFiltering a BindingSource based on the number of child rows
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  1. POFiltering a BindingSource based on the number of child rows
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    copied!<p>I'm working on my first little Database application where I use a typed <code>DataSet</code> and data binding:</p> <p><img src="https://i.stack.imgur.com/V4fBr.png" alt="enter image description here"></p> <p>I have a <code>customersBindingSource</code> to bind the list of customers to the <code>ListBox</code> on the left and an <code>allowedclientsBindingSource</code> to bind the list of allowed clients (of the selected customer) to the <code>DataGridView</code> on the right.</p> <p>Now I'd like to apply a filter so that only disabled clients are shown on the right. I can do that by setting </p> <pre><code>allowedclientsBindingSource.Filter = "Enabled = 'false'"; </code></pre> <p>and this works fine. Now not all customers have disabled clients. And I want to show only those customers on the left which actually have disabled clients. So I'm looking for something like this:</p> <pre><code>customersBindingSource.Filter = "numberOfAllowedClients &gt; 0"; </code></pre> <p>Of course this <code>numberOfAllowedClients</code> must refer to the <em>filtered</em> list of allowed clients.</p> <p>What is the correct filter expression to achieve this?</p> <p><strong>Edit:</strong></p> <p>If possible I'd like to keep using data binding and not filling the <code>ListBox</code> manually.</p> <p>What I found is that I can filter the customers list based on the number of child rows like this:</p> <pre><code>customersBindingSource.Filter = "Count(Child.AllowedClientID) &gt; 0"; </code></pre> <p>but it uses the unfiltered list of clients. I also tried:</p> <pre><code>customersBindingSource.Filter = "Count(Child.Enabled = 'false') &gt; 0"; </code></pre> <p>but this doesn't work since no expressions are allowed in the <code>Count</code> aggregate. I also tried to set the <code>RowFilter</code> property on the <code>DefaultView</code> of the data table instead of on the binding source. But that didn't work either.</p> <p>Is there really no clean and easy solution for this without doing it manually?</p>
 

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