# How to validate if a license was revoked on the server?

As of version QLM12, please follow the instructions in this [article](/docs/fundamental-concepts/server-side-license-validation.md).

To verify if a license was revoked on the server or if a license is illegal, add the code below to your application. If you are using the **LicenseValidator** class generated by the Protect Your Application wizard, simply set the **checkIfLicenseIsRevoked** property to true.

You can find the definition of an "Illegal Computer" in the QLM online help.

To revoke a license, locate the license in the Manage Keys tab, click on the Edit button and check the "Disabled" checkbox.

{% tabs %}
{% tab title="C#" %}
{% code overflow="wrap" %}

```csharp
public bool VerifyLicenseOnServer ()
{
bool ret = false;
string webServiceUrl = "https://qlm3.net/qlmdemo/qlmLicenseServer/qlmservice.asmx";

string response;
string qlmVersion = "6.0.00";
string storedActivationKey = string.Empty;
string storedComputerKey = string.Empty;
string computerID = System.Environment.MachineName;
string computerName = System.Environment.MachineName;


QLM.LicenseValidator lv = new QLM.LicenseValidator();
lv.QlmLicense.ReadKeys(ref storedActivationKey, ref storedComputerKey);

if (!String.IsNullOrEmpty(storedActivationKey))
{

    if (lv.QlmLicense.IsLicenseKeyRevoked(webServiceUrl, storedActivationKey))
    {
        MessageBox.Show(String.Format ("License key {0} was revoked.", storedActivationKey));
    }
    else if (lv.QlmLicense.IsIllegalComputer(webServiceUrl, storedActivationKey, storedComputerKey, computerID, computerName, qlmVersion, out response))
    {
        ILicenseInfo li = new LicenseInfo();
        string message = string.Empty;
        lv.QlmLicense.ParseResults(response, ref li, ref message);
        MessageBox.Show("Illegal Computer License: " + message);
    }
    else
    {
        ret = true;
    }            
}
return ret;
}
```

{% endcode %}
{% endtab %}

{% tab title="VB.NET" %}

<pre class="language-vbnet" data-overflow="wrap"><code class="lang-vbnet"><strong>Public Function VerifyLicenseOnServer() As Boolean
</strong>Dim ret As Boolean = False
Dim webServiceUrl As String = "https://qlm3.net/qlmdemo/qlmLicenseServer/qlmservice.asmx"
Dim response As String = String.Empty
Dim qlmVersion As String = "6.0.00"
Dim storedActivationKey As String = String.Empty
Dim storedComputerKey As String = String.Empty
Dim computerID As String = Environment.MachineName
Dim computerName As String = Environment.MachineName

Dim lv As New QLM.LicenseValidator()
lv.QlmLicenseObject.ReadKeys(storedActivationKey, storedComputerKey)

If Not String.IsNullOrEmpty(storedActivationKey) Then
    If lv.QlmLicenseObject.IsLicenseKeyRevoked(webServiceUrl, storedActivationKey) Then
        MessageBox.Show(String.Format("License key {0} was revoked.", storedActivationKey))
    ElseIf lv.QlmLicenseObject.IsIllegalComputer(webServiceUrl, storedActivationKey, storedComputerKey, computerID, computerName, qlmVersion, response) Then
        Dim li As ILicenseInfo = New LicenseInfo()
        Dim message As String = String.Empty
        lv.QlmLicenseObject.ParseResults(response, li, message)
        MessageBox.Show("Illegal Computer License: " &#x26; message)
    Else
        ret = True
    End If
End If

Return ret
</code></pre>

End Function
{% endtab %}
{% endtabs %}


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