Argument Cannot Be Nulled Error

Question

I am receiving an "Argument cannot be nulled error" when I add an attempt to set searchString to String.escapeSingleQuotes(preEscape) in my class. The error appears upon loading the VF page. The VF page does not load when I add in the line that sets searchString to the above.

I believe the error is because String.escapeSingleQuotes cannot handle a null string, but where I would I set the value of the preEscape string? I attempted to set it at the beginning of the controller but it won't let me set the string unless I am in a method.

VF Page:

<apex:page controller="myClass" showHeader="true">
    <apex:inputText id="searchString" value="{!preEscape}" onkeypress="return noenter(event);"/>
    <apex:commandButton title="Search" value="Search" onclick="searchAccounts(); return false;"/>
</apex:page>

Controller:

public class myClass {
    Public string preEscape{get;set;}
    Public string searchString{get;set;}
    public string searchType{get;set;}
    public string searchWhere{get;set;}
    public boolean searchLastName{get;set;}


public void searchAccounts() {
searchString = String.escapeSingleQuotes(preEscape);
if(searchType == 'lastNameSearch') {
  searchWhere = 'Client_Last_Name__c = \''+ searchString +'\'';
  searchLastName = true;
}
}
}

Answer 1

You don't need to escape the characters if you simply use a binding statement:

searchWhere = 'Client_Last_Name__c = :preEscape';

For sake of argument, if you did need to escape it, check for a null value first:

if(preEscape != null) {
    searchString = String.escapeSingleQuotes(preEscape);
}