<div>
I suspect you have the following DLL, DocumentFormat.OpenXml.dll<wbr />, added to your references in your application but do you have the following using statements
<pre><code class="code-1 nolinks" id="code-20-41729400-1"><span>using DocumentFormat.OpenXml.Packaging;</span>
<span>using DocumentFormat.OpenXml.Spreadsheet;</span>
</code></pre>
</div>


<div>
How to correct<br />

<pre><code class="code-1 nolinks" id="code-20-41730527-1"><span>Error	2	'DocumentFormat.OpenXml.Packaging.SpreadsheetDocument' does not contain a definition for 'Worksheets' and no extension method 'Worksheets' accepting a first argument of type 'DocumentFormat.OpenXml.Packaging.SpreadsheetDocument' could be found (are you missing a using directive or an assembly reference?)</span>
</code></pre>
due to last line below?<br />

<pre><code class="code-1 nolinks" id="code-20-41730527-2"><span>                    using (SpreadsheetDocument Book0 = SpreadsheetDocument.Open(openFileDialog1.FileName, true))</span>
<span>                    {</span>
<span></span>
<span>                        Worksheet0 = (Excel.Worksheet)Book0.Worksheets.Add();</span>
</code></pre>
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<div>
Yes, I did.<br />
<br />
How to add one new Worksheet to WorkbookPart below?<br />

<pre><code class="code-1 nolinks" id="code-20-41730647-1"><span>                        foreach (Excel.Worksheet sheet in Book0.WorkbookPart.Workbook.Descendants&lt;Sheet&gt;().Where(s =&gt; s.Name == Worksheet0))</span>
<span>                        {</span>
<span>                            ...</span>
</code></pre>
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<div>
Seeming you are no longer having the original problem you have posted in this question. Please close this thread by assigning the points to the solution that solved the issue and opening a new question for your last post. Thanks.
</div>


<div>
These two links should answer your last question.<br />
<br />
<a href="https://blogs.msdn.microsoft.com/chrisrae/2011/08/18/creating-a-simple-xlsx-from-scratch-using-the-open-xml-sdk/" rel="ugc">Creating a simple XLSX from scratch using the Open XML SDK</a><br />
<a href="https://msdn.microsoft.com/en-us/library/office/documentformat.openxml.packaging.spreadsheetdocument.aspx" rel="ugc">SpreadsheetDocument class</a>
</div>


<div>
Thanks a lot.<br />
How to resolve<br />

<pre><code class="code-1 nolinks" id="code-20-41732239-1"><span>Error	3	Cannot implicitly convert type 'Microsoft.Office.Interop.Excel.Sheets' to 'DocumentFormat.OpenXml.Spreadsheet.Worksheet'. An explicit conversion exists (are you missing a cast?)	C:\App\WindowsFormsApplication5\WindowsFormsApplication2\Form1.cs	237	71	WindowsFormsApplication2</span>
<span>Error	4	The type 'Microsoft.Office.Interop.Excel.Sheets' cannot be used as type parameter 'T' in the generic type or method 'DocumentFormat.OpenXml.OpenXmlElement.GetFirstChild&lt;T&gt;()'. There is no implicit reference conversion from 'Microsoft.Office.Interop.Excel.Sheets' to 'DocumentFormat.OpenXml.OpenXmlElement'.	C:\App\WindowsFormsApplication5\WindowsFormsApplication2\Form1.cs	237	71	WindowsFormsApplication2</span>
<span>Error	5	'Sheets' is an ambiguous reference between 'Microsoft.Office.Interop.Excel.Sheets' and 'DocumentFormat.OpenXml.Spreadsheet.Sheets'	C:\App\WindowsFormsApplication5\WindowsFormsApplication2\Form1.cs	237	119	WindowsFormsApplication2</span>
</code></pre>
<br />
due to this line?<br />

<pre><code class="code-1 nolinks" id="code-20-41732239-2"><span>                DocumentFormat.OpenXml.Spreadsheet.Worksheet sheets = spreadSheet.WorkbookPart.Workbook.GetFirstChild&lt;Sheets&gt;();</span>
</code></pre>
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<div>
Sorry but I have not worked with Excel through code.
</div>


<div>
<div class="content wysiwyg-content">
Hi,<br />
How to correct this<br />

<pre><code class="code-1 nolinks" id="code-10-28959541-1"><span>Error	2	'DocumentFormat.OpenXml.Packaging.SpreadsheetDocument' does not contain a definition for 'WorksheetParts' and no extension method 'WorksheetParts' accepting a first argument of type 'DocumentFormat.OpenXml.Packaging.SpreadsheetDocument' could be found (are you missing a using directive or an assembly reference?)</span>
</code></pre>
<br />
due to 2nd line below?<br />
<br />

<pre><code class="code-1 nolinks" id="code-10-28959541-2"><span>                    SpreadsheetDocument Book0 = SpreadsheetDocument.Open(openFileDialog1.FileName, false);</span>
<span>                    WorksheetPart worksheetPart = Book0.WorksheetParts.First();</span>
</code></pre>
</div>
</div>


Hi,
How to correct this
(CODE)

due to 2nd line below?

(CODE)

Problem to DocumentFormat

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