Well-formed XML error when saving the sharepoint custom web part using web services

Question

I created a custom web part that has a custom collection property (Tabs). The web part works properly when you edit and save the custom property on edit mode (via browser). I want to update my custom web part using web services,so I exported the web part and took the xml content and passed it as it is (so I could easily test it), but an error occured

The file you imported is not valid. 
Verify that the file is a Web Part description file (*.webpart or *.dwp) and that it contains well-formed XML.

I have already validated the xml using online xml validator and removed this statement

<?xml version="1.0" encoding="utf-16"?>

as this is the one causing the not well-formex XML according to XML validator, but still no luck, same error occured.

Any Ideas? I could not figured it out what's wrong with the XML specially on Tabs property.

Code:

    string webPartXml = string.Empty;
    string pageUrl = currenturl;

        Guid storageKey = new Guid(webpartid);

        using (StreamReader sr = new StreamReader(@"C:\tab.txt"))
        {            
            webPartXml = sr.ReadToEnd();                
        }
        webPartXml = webPartXml.Replace("&lt;", "<").Replace("&gt;",">");

        try
        {
            svc.SaveWebPart2(pageUrl, storageKey, webPartXml, WebpartpagesSvc.Storage.Shared, false);
        }catch(Exception err)
        {
            throw;
        }

Tab.txt (Tab.webpart)

<webParts>
  <webPart xmlns="http://schemas.microsoft.com/WebPart/v3">
    <metaData>
      <type name="Test.TabWebPart, Test, Version=1.0.0.0, Culture=neutral, PublicKeyToken=c9e6068352095bx6" />
      <importErrorMessage>Cannot import this web part.</importErrorMessage>
    </metaData>
    <data>
      <properties>
        <property name="ChromeType" type="chrometype">None</property>
        <property name="Height" type="unit" />
        <property name="PanelHeight" type="int">0</property>
        <property name="ShowRoundedTabs" type="bool">False</property>
        <property name="AllowZoneChange" type="bool">True</property>
        <property name="AllowEdit" type="bool">True</property>
        <property name="Tabs" type="Test.Tabs, Test, Version=1.0.0.0, Culture=neutral, PublicKeyToken=c9e6068352095bx6">&lt;?xml version="1.0" encoding="utf-16"?&gt;
&lt;Tabs xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"&gt;
  &lt;TabInfo&gt;
    &lt;Tab&gt;
      &lt;Title&gt;HTML-TESTING&lt;/Title&gt;     
    &lt;/Tab&gt;
  &lt;/TabInfo&gt;
&lt;/Tabs&gt;</property>
        <property name="CatalogIconImageUrl" type="string" />
        <property name="PanelWidth" type="int">0</property>
        <property name="AllowConnect" type="bool">True</property>
        <property name="AllowClose" type="bool">True</property>
        <property name="HelpMode" type="helpmode">Navigate</property>
        <property name="ChildTab" type="System.Collections.Specialized.NameValueCollection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934ebb9" />
        <property name="Hidden" type="bool">False</property>
        <property name="Title" type="string">Tab </property>
        <property name="ChromeState" type="chromestate">Normal</property>
        <property name="AllowHide" type="bool">True</property>
        <property name="Description" type="string">for Tab Sample.</property>
        <property name="AllowMinimize" type="bool">True</property>
        <property name="TitleUrl" type="string" />
        <property name="Width" type="unit" />
        <property name="ExportMode" type="exportmode">All</property>
        <property name="Direction" type="direction">NotSet</property>
        <property name="HelpUrl" type="string" />
        <property name="TitleIconImageUrl" type="string" />
      </properties>
    </data>
  </webPart>
</webParts>

Error Message

base {System.SystemException} = {"Exception of type 'Microsoft.SharePoint.SoapServer.SoapServerException' was thrown."}
InnerText = "The file you imported is not valid. Verify that the file is a Web Part description file (*.webpart or *.dwp) and that it contains well-formed XML."
InnerXml = "<errorstring xmlns=\"http://schemas.microsoft.com/sharepoint/soap/\">The file you imported is not valid. Verify that the file is a Web Part description file (*.webpart or *.dwp) and that it contains well-formed XML.</errorstring>"

Answer 1

Write the code of below in Module's Element.xml & change only your list name in listUrl & TitleUrl

<Module>
<File>
<AllUsersWebPart WebPartZoneID="wzMain" WebPartOrder="2">
    <![CDATA[
    <webParts>
    <webPart xmlns="http://schemas.microsoft.com/WebPart/v3">
    <metaData>
    <type name="Microsoft.SharePoint.WebPartPages.XsltListViewWebPart, Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" />
    <importErrorMessage>Cannot import this Web Part.</importErrorMessage>
    </metaData>
    <data>
    <properties>
    <property name="ShowWithSampleData" type="bool">False</property>
    <property name="Default" type="string" />
    <property name="NoDefaultStyle" type="string" null="true" />
    <property name="CacheXslStorage" type="bool">True</property>
    <property name="ViewContentTypeId" type="string" />
    <property name="XmlDefinitionLink" type="string" />
    <property name="ManualRefresh" type="bool">False</property>
    <property name="ListUrl" type="string" >Lists/Employee_list</property>
    <property name="TitleUrl" type="string">/Lists/Employee_list</property>
    </properties>
    </data>
    </webPart>
    </webParts>
    ]]>
    </AllUsersWebPart>
    </File>
  </Module>

Answer 2

I think it is when you try to restore the xml to original that breaks it. Do you really need this line of code:

webPartXml = webPartXml.Replace("&lt;", "<").Replace("&gt;",">"); 

What happens if you remove it? If it doesnt work, I would recommend wrapping the value in CDATA-tag in order to escape the xml:

string startTabProperty = @"<property name=""Tabs"" type=""Test.Tabs, Test, Version=1.0.0.0, Culture=neutral, PublicKeyToken=c9e6068352095bx6"">";
string endTabProperty = "></property>"; //Note the >< in order to identify correct place
webPartXml = webPartXml.Replace("&lt;", "<").Replace("&gt;",">"); 
webPartXml = webPartXml.Replace(startTabProperty, startTabProperty + "<![CDATA[");
webPartXml = webPartXml.Replace(endTabProperty , ">" + "]]>" + "</property>");

Good luck!