Hello, everyone! 

I have a trouble with sorting in VF page controller. The problem is: the sort doesn't work. The records are sorted in the way i set in constructor. And i need to sort using the selected field from a list

------------------------------VF Page--------------------------------------------

<apex:page standardController="BShop__c" standardStylesheets="true" showHeader="true" sidebar="false" extensions="tablesorting">

<apex:form >
<br><h1>click <apex:commandLink value="HERE" action="https://c.ap1.visual.force.com/apex/searchSheet" /> to pass to the search page</h1></br>
</apex:form>
<apex:form >
<br></br>
<apex:pageBlock >

<apex:pageBlockSection >


<apex:pageBlockSectionItem >
<apex:outputLabel >Name</apex:outputLabel>
<apex:inputField id="Name" value="{!BShop__c.Name}"/>
</apex:pageBlockSectionItem>

<apex:pageBlockSectionItem >
<apex:outputLabel >ReleaseDate</apex:outputLabel>
<apex:inputField id="ReleaseDate" value="{!BShop__c.ReleaseDate__c}"/>
</apex:pageBlockSectionItem>

<apex:pageBlockSectionItem >
<apex:outputLabel >Type</apex:outputLabel>
<apex:inputField id="Type" value="{!BShop__c.Type__c}"/>
</apex:pageBlockSectionItem>

<apex:pageBlockSectionItem >
<apex:outputLabel >AdditionDate</apex:outputLabel>
<apex:inputField id="AdditionDate" value="{!BShop__c.AdditionDate__c}"/>
</apex:pageBlockSectionItem>

<apex:pageBlockSectionItem >
<apex:outputLabel >Price</apex:outputLabel>
<apex:inputField id="Price" value="{!BShop__c.Price__c}"/>
</apex:pageBlockSectionItem>

<apex:pageBlockSectionItem >
<apex:outputLabel >Available</apex:outputLabel>
<apex:inputField id="Available" value="{!BShop__c.Available__c}"/>
</apex:pageBlockSectionItem>

<apex:pageBlockSectionItem >
<apex:outputLabel >Total</apex:outputLabel>
<apex:inputField id="Total" value="{!BShop__c.Total__c}"/>
</apex:pageBlockSectionItem>
</apex:pageBlockSection>

<apex:pageBlockButtons >
<apex:commandButton id="Save" action="{!quickSave}" value="Save"/>
<apex:commandButton id="Cancel" action="{!Cancel}" value="Cancel"/>
</apex:pageBlockButtons>

</apex:pageBlock>
</apex:form>
<apex:form >
<apex:pageBlock >

<apex:selectList value="{!selectedField }" size="1">
<apex:selectOption itemValue="BShop__c.Name" itemLabel="Name"/>
<apex:selectOption itemValue="BShop__c.Type__c" itemLabel="Type"/>
<apex:selectOption itemValue="BShop__c.ReleaseDate__c" itemLabel="The Date of Release"/>
</apex:selectList>

<apex:commandButton value="Sort Table" action="{!sortMethod}"/>


<apex:pageblocktable value="{!tablesort}" var="rec">
<apex:column value="{!rec.Name}"/>
<apex:column value="{!rec.Type__c}"/>
<apex:column value="{!rec.Price__c}"/>
<apex:column value="{!rec.Total__c}"/>
<apex:column value="{!rec.ReleaseDate__c}"/>
<apex:column value="{!rec.AdditionDate__c}"/>
<apex:column value="{!rec.Available__c}"/>
</apex:pageblocktable>
</apex:pageBlock>

</apex:form>

</apex:page>

----------------------------apex class-----------------------------

Public with sharing class tablesorting {
public list<BShop__c> tablevar{get;set;}
Public string selectedField {get;set;}
public list<BShop__c> tablesort{get;set;}

public tablesorting(ApexPages.StandardController BShop){

tablesort = [SELECT Name, Type__c, Price__c, Total__c, ReleaseDate__c, AdditionDate__c, Available__c FROM BShop__c ORDER BY Name ];
}

public void sortMethod(){

if(selectedField == 'Name')
tablesort = [SELECT Name, Type__c, Price__c, Total__c, ReleaseDate__c, AdditionDate__c, Available__c FROM BShop__c ORDER BY Name ];
else if(selectedField == 'Type__c')
tablesort = [SELECT Name, Type__c, Price__c, Total__c, ReleaseDate__c, AdditionDate__c, Available__c FROM BShop__c ORDER BY Type__c ];
else if(selectedField == 'ReleaseDate__c')
tablesort = [SELECT Name, Type__c, Price__c, Total__c, ReleaseDate__c, AdditionDate__c, Available__c FROM BShop__c ORDER BY ReleaseDate__c ];
}
}