# C1.LiveLinq.Collections.IndexedCollection-1.BeginUpdate

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<h1 id="C1_LiveLinq_Collections_IndexedCollection_1_BeginUpdate_" data-uid="C1.LiveLinq.Collections.IndexedCollection`1.BeginUpdate*">BeginUpdate Method
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<h4 id="C1_LiveLinq_Collections_IndexedCollection_1_BeginUpdate" data-uid="C1.LiveLinq.Collections.IndexedCollection`1.BeginUpdate">BeginUpdate()</h4>
<div class="markdown level1 summary"><p>Suspends notifications while massive changes are being made to the <a class="xref" href="C1.LiveLinq.Collections.IndexedCollection-1.html">IndexedCollection&lt;T&gt;</a>.</p>
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<h5 class="declaration">Declaration</h5>
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  <pre><code class="lang-csharp hljs">public void BeginUpdate()</code></pre>
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  <pre><code class="lang-vbnet hljs">Public Sub BeginUpdate()</code></pre>
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<h5 id="C1_LiveLinq_Collections_IndexedCollection_1_BeginUpdate_remarks">Remarks</h5>
<div class="markdown level1 remarks"><p>This method must be followed by <a class="xref" href="C1.LiveLinq.Collections.IndexedCollection-1.EndUpdate.html#C1_LiveLinq_Collections_IndexedCollection_1_EndUpdate">EndUpdate()</a>.</p>
<p>Use this method when you already have indexes built over the <a class="xref" href="C1.LiveLinq.Collections.IndexedCollection-1.html">IndexedCollection&lt;T&gt;</a> or live views based on it,
and you need to re-populate this <a class="xref" href="C1.LiveLinq.Collections.IndexedCollection-1.html">IndexedCollection&lt;T&gt;</a> or perform other massive changes to items of this collection.
Without this method, every single change you make causes LiveLinq to perform necessary operations
for maintaining your indexes and live views dependent on this collection. In case of massive changes,
this can be slower than to wait until the massive changes are done and rebuild the indexes and live views.</p>
<p> Between <b>BeginUpdate</b> and <a class="xref" href="C1.LiveLinq.Collections.IndexedCollection-1.EndUpdate.html#C1_LiveLinq_Collections_IndexedCollection_1_EndUpdate">EndUpdate()</a> calls, indexes, live views, bound controls
and other change notification listeners are not updated, they don't receive change notifications.</p>
<p>When <a class="xref" href="C1.LiveLinq.Collections.IndexedCollection-1.EndUpdate.html#C1_LiveLinq_Collections_IndexedCollection_1_EndUpdate">EndUpdate()</a> is called, a 
<a class="xref" href="C1.LiveLinq.SourceChangeType.html">SourceChangeType.Modify</a> or <a class="xref" href="C1.LiveLinq.SourceChangeType.html">SourceChangeType.Reset</a>
notification is sent, depending on whether the change affected a single item or multiple items of the collection.
Even when you change a single item, it may make sense to enclose your changes in <b>BeginUpdate/EndUpdate</b> if
you change multiple properties of the item. In that case a <a class="xref" href="C1.LiveLinq.SourceChangeType.html">SourceChangeType.Modify</a>
notification is sent. If more than one item was changed, a <a class="xref" href="C1.LiveLinq.SourceChangeType.html">SourceChangeType.Reset</a>
notification is sent, meaning all indexes, live views and other collections dependent on this data table
must be rebuilt from scratch.</p>
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