Get all Wsp from SPFarm using PowerShell

(Get-SPFarm).Solutions | ForEach-Object{$var = "Folder Path" + "\" + $_.Name;$_.SolutionFile.SaveAs($var)}

Get SPGroup users in SharePoint programmatically

 SPGroup UserGroup = OWeb.Groups["User Group Name"];
 if (UserGroup.Users.Count > 0)
  {
     foreach (SPUser User in UserGroup.Users)
     {
        string UserName=User.LoginName;
     }
  }

Adding and Deploying solution using powershell in SharePoint

Add Solution:

add-SPSolution "wsp file path"

Deploy Solution:

Install-SPSolution –Identity "example.wsp" –WebApplication "http://sp2013" -GACDeployment

Update Solution:

Update-SPSolution –Identity "example.wsp" –LiteralPath "Wsp path" –GACDeployment

Retract Solution:

Uninstall-SPSolution –Identity "Example.wsp" –WebApplication "http://sp2013"

Remove Solution:

Remove-SPSolution –Identity "Example.wsp"

Get all user name and id in web using powershell

Get-SPUser -web "Site Url" | ForEach-Object{ ""+ $_.Id+""+$_.Name}

Check current user in SPFieldUser collection

SPFieldUserValueCollection usercoll= new SPFieldUserValueCollection(oweb, item["usercoll"].ToString());
bool containuser=likedBy.Find(u => u.User.LoginName.ToString().Contains(SPContext.Current.Web.CurrentUser.LoginName))!= null ? true : false;