#Initializing Assemblies.
$scriptDir =  Split-Path $script:MyInvocation.MyCommand.Path
Write-Host "Current script directory is $scriptDir"
Add-Type -Path "$scriptDir\Microsoft.IdentityModel.Clients.ActiveDirectory.dll";
Add-Type -Path "$scriptDir\Microsoft.Xrm.Sdk.dll"
Add-Type -Path ([Reflection.Assembly]::LoadWithPartialName("System.IO")).Location;
Add-Type -Path ([Reflection.Assembly]::LoadWithPartialName("System.Net")).Location;
Add-Type -Path ([Reflection.Assembly]::LoadWithPartialName("System.Threading.Tasks")).Location;
Add-Type -Path ([Reflection.Assembly]::LoadWithPartialName("System.Security")).Location;
Add-Type -Path ([Reflection.Assembly]::LoadWithPartialName("System.Text.Encoding")).Location;
Add-Type -Path ([Reflection.Assembly]::LoadWithPartialName("System.Text.Encoding")).Location;

#Process Configuration.
$crmInstance = "https://crmcrate.crm.dynamics.com";
$crmClientId = "YOUR CLIENT ID";
$crmClientSecret = "YOUR SECRET ID";
      
#Initiliazing CRM S2S Service Proxy.
function GetS2SService()
{
    [System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12;
    $clientcred = New-Object Microsoft.IdentityModel.Clients.ActiveDirectory.ClientCredential -ArgumentList ($CrmClientId, $CrmClientSecret);
    $authenticationContext = New-Object Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext -ArgumentList ("https://login.microsoftonline.com/dr36214hc-fre7-d567-c0y2-222f6fd0g30c");
    $authenticationContext.TokenCache.Clear();
    $authenticationResult = $authenticationContext.AcquireTokenAsync($CrmInstance, $clientcred).Result;
    $urlXRMSDK = New-Object System.Uri -ArgumentList ("$CrmInstance/xrmservices/2011/organization.svc/web?SdkClientVersion=8.2");
    $_service = New-Object Microsoft.Xrm.Sdk.WebServiceClient.OrganizationWebProxyClient -ArgumentList ($urlXRMSDK, [System.TimeSpan]::MaxValue , $false);
    $_service.HeaderToken = $authenticationResult.AccessToken;
    return $_service;
}

#Initializing Web Proxy.
function GetS2SServiceOrgWebProxy()
{
    $svc = $null;   
    Write-Host "Connecting to CRM $CrmInstance";
    $svc = GetS2SService;
    return $svc;
}

#Main Method.
function Main (){
    $counter = 0;
Write-Host "Connecting to the CRM $CrmInstance ";
try{
    $svc = GetS2SServiceOrgWebProxy;
     
     #Fetch XML For Retrieving Event Process Records.
    $fetchEventProcessor = @("<fetch version='1.0' output-format='xml-platform' mapping='logical' distinct='false'>
    <entity name='account'>
    <attribute name='accountnumber' />
    <attribute name='accountname' />
    <attribute name='accountid' />
    <filter type='and'>
    <condition attribute='accountnumber' operator='eq' value='1000' />
    </filter>
    </entity>
    </fetch>");
    $fetchEventProcessor = [string]::Format($fetchEventProcessor);

    #FetchExpression  object
    $fetchExpression = New-Object Microsoft.Xrm.Sdk.Query.FetchExpression -ArgumentList ($fetchEventProcessor);

    #get EntityCollection
    $objAccountData = $svc.RetrieveMultiple($fetchExpression);

    #Verifying Count Of Retrieved Records.
    if ($objAccountData.Entities.Count -gt 0)
    {
        $recordCount = $objAccountData.Entities.Count;
        Write-Host "Total Number Of Account Records : $recordCount";
    foreach ($accountRecord in $objAccountData.Entities)
    {
    $accountId = $accountRecord.Id;
    #Declaring Entity.
    $eMail = New-Object Microsoft.Xrm.Sdk.Entity("email")
    $eFromActivityParty = New-Object Microsoft.Xrm.Sdk.Entity("activityparty")
    $eToActivityParty = New-Object Microsoft.Xrm.Sdk.Entity("activityparty")
    $guid = $accountRecord.Attributes["accountid"];

    #Creating User Object (To Email).
    $lookupObjectA = New-Object -TypeName Microsoft.Xrm.Sdk.EntityReference;
    $lookupObjectA.LogicalName = "systemuser";
    $lookupObjectA.Id = "1f6311ff-r218-f922-a9h6-111d3a454d54";

    #Creating User Object (From Email).
    $lookupObjectB = New-Object -TypeName Microsoft.Xrm.Sdk.EntityReference;
    $lookupObjectB.LogicalName = "systemuser";
    $lookupObjectB.Id = "zx461rff-f238-h922-a9h6-111d3a454d54";
 
    $eFromActivityParty["partyid"] =  [Microsoft.Xrm.Sdk.EntityReference] $lookupObjectA;
    $eToActivityParty["partyid"] = [Microsoft.Xrm.Sdk.EntityReference] $lookupObjectB; 

    #Setting Up Attributes.
    $eMail["from"] = New-Object Microsoft.Xrm.Sdk.Entity $eFromActivityParty;
    $eMail["to"] = New-Object Microsoft.Xrm.Sdk.Entity  $eToActivityParty ;
    $eMail["subject"] = "Testing Subject";
    $eMail["description"] = "Testing Decription";
    $eMail["regardingobjectid"] = New-Object Microsoft.Xrm.Sdk.EntityReference -ArgumentList ("account",$accountId);

    #Initiating Email.
    $emailId = $svc.Create($eMail);
    $sendEmailRequest = New-Object  Microsoft.Xrm.Sdk.SendEmailRequest {
      EmailId = $emailId,
      TrackingToken = "",
      IssueSend = $true
    };

    #Sending Final Email Activity Request.
    $sendEmailresp = Microsoft.Xrm.Sdk.SendEmailResponse $svc.Execute($sendEmailRequest);
    }
    }  
}
catch 
{
    Write-Host "$_.Message";
}
}

Main;