How to hide public methods from IntelliSense

Using the EditorBrowsable attribute like so will cause a method not to be shown in IntelliSense:

[System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
public void MyMethod()
{
}

You are looking for EditorBrowsableAttribute

The following sample demonstrates how to hide a property of a class from IntelliSense by setting the appropriate value for the EditorBrowsableAttribute attribute. Build Class1 in its own assembly.

In Visual Studio, create a new Windows Application solution, and add a reference to the assembly which contains Class1. In the Form1 constructor, declare an instance of Class1, type the name of the instance, and press the period key to activate the IntelliSense drop-down list of Class1 members. The Age property does not appear in the drop-down list.

using System;
using System.ComponentModel;

namespace EditorBrowsableDemo
{
    public class Class1
    {
        public Class1()
        {
            //
            // TODO: Add constructor logic here
            //
        }

        int ageval;

        [EditorBrowsable(EditorBrowsableState.Never)]
        public int Age
        {
            get { return ageval; }
            set
            {
                if (!ageval.Equals(value))
                {
                    ageval = value;
                }
            }
        }
    }
}