Could You please help me i want to get pick list values the field name is {!A.Online_Courses__c} how i get in this code?

Question

Visualforce code:

<apex:page controller="OnlineAdmission">
    <apex:form>
        <style>
            tr.dr1 {
                background-color: #CCFF66;
                color: blue;
                font-size: 20px
            }
            tr.dr3 {
                background-color: Yellow;
                color: blue;
                font-size: 20px
            }
            tr.dr1:hover {
                background-color: #00FFFF;
            }
            tr.dr3:hover {
                background-color: #FF3397;
            }
        </style>
        <apex:pageBlock>
            <table class="List" border="0" cellpadding="5" cellspacing="1">
                <tr class="dr3">
                    <th>Welcome to Devry University</th>
                    <th>Main Branch office</th>
                </tr>
                <tr class="dr1">
                    <td>Candidate Name:</td>
                    <td>
                        <apex:inputtext value="{!A.Candidate_Name__c}" />
                    </td>
                </tr>
                <tr class="dr1">
                    <td>Online Courses:</td>
                    <td>
                        <apex:selectlist value="{!A.Online_Courses__c}" />
                    </td>
                </tr>
                <apex:pageBlockButtons>
                    <apex:commandButton value="Save" action="{!save}" />
                    <apex:commandButton value="Save&New" action="{!savenew}" />
                </apex:pageBlockButtons>
            </table>
        </apex:pageBlock>
    </apex:form>
</apex:page>

Apex Code:

public class OnlineAdmission { 
public Obj_A__c A{set;get;} 
public list<Obj_A__c> B {set;get;}

 public OnlineAdmission() { 
    A=new Obj_A__c(); 
    B=[select id,Online_Courses__c from Obj_A__c ]; 
 } 

    public pagereference save() { 
        insert A; 

        pagereference pg=new pagereference('/'+A.id); 
        return pg; 
        } 

        public void savenew() {
            insert A; A.clear(); 
        }
}

Answer 1

If you change your Visualforce code from a apex:selectList to an apex:inputField the Visualforce engine will take care of rendering the correct picklist values.

Change:

<apex:selectlist value="{!A.Online_Courses__c}" />

To:

<apex:inputField value="{!A.Online_Courses__c}" />

Alternatively, if you still need to use an apex:selectList, you can use Apex Describe to get the values.

In the controller:

public List<SelectOptions> courseOptions { get; set; }
public String selectedCourse { get; set; }

public OnlineAdmission() {
    Schema.DescribeFieldResult dfr = Obj_A__c.Online_Courses__c.getDescribe();
    List<Schema.PicklistEntry> entries = dfr.getPicklistValues();

    List<SelectOption> coursesOptions = new List<SelectOption>();
    for (Schema.PicklistEntry entry : entries) {
        coursesOptions.add( new SelectOption(entry.getValue(), entry.getLabel()) );
    }
}

In the page:

<apex:selectList value="{!selectedCourse}" multiselect="false" size="1">
    <apex:selectOptions value="{!courseOptions"}/>
</apex:selectList>