Check for null/empty in dictionary
Each of these:

string account = string.Empty;

if (queryWhere.ContainsKey("account") 
   &amp;&amp; queryWhere["account"] != null 
   &amp;&amp; !string.IsNullOrEmpty(queryWhere["account"].ToString()))
{
    account = queryWhere["account"].ToString();
}


Should be reduced to:

string account;
if(!queryWhere.TryGetValue("account", out account))
{
   account = string.Empty; // if you need the string to be empty // default is null
}


Dictionary.TryGetValue

But that logic can then be moved to a method:

private string GetValue(string key)
{
   string returnValue;
   if(!queryWhere.TryGetValue(key, out returnValue))
   {
      returnValue= string.Empty;
   }
   return returnValue;
}

string account = GetValue("account");
string customer = GetValue("customer");




I really don't see the point of your original code, BTW. For instance, the .ToString() is completely superfluous, since you're working with a Dictionary&lt;string,string&gt;. It is always going to return a string.

But why do you even check for string.IsNullOrEmpty()? You already know it isn't null from the previous line's check -- queryWhere["account"] != null -- so at worst it is empty which is your default value anyway!