How to Fix CS1061 'Does Not Contain Definition' Error in C#

The CS1061 error means you are trying to use a method or property that does not exist on the object or type. To fix it, check the spelling, ensure the member exists, and verify you are using the correct type or namespace with using directives.

Why This Happens

This error happens when you try to call a method or access a property that the object or class does not have. It can be due to a typo, missing method, or using the wrong type. The compiler cannot find the member you want to use.

csharp

using System;

public class Car {
    public void Drive() {
        Console.WriteLine("Driving");
    }
}

class Program {
    static void Main() {
        Car myCar = new Car();
        myCar.DriveFast(); // Error: CS1061
    }
}

Output

error CS1061: 'Car' does not contain a definition for 'DriveFast' and no accessible extension method 'DriveFast' accepting a first argument of type 'Car' could be found

The Fix

To fix this error, make sure the method or property you want to use actually exists on the object. Correct any typos and confirm you are calling the right member. If needed, add the missing method or use the correct type.

csharp

using System;

public class Car {
    public void Drive() {
        Console.WriteLine("Driving");
    }

    public void DriveFast() {
        Console.WriteLine("Driving fast!");
    }
}

class Program {
    static void Main() {
        Car myCar = new Car();
        myCar.DriveFast(); // Works now
    }
}

Output

Driving fast!

Prevention

To avoid this error, always check your spelling carefully. Use your IDE's autocomplete to see available members. Make sure you have the right using statements for namespaces. Keep your classes and methods well organized and documented.

Related Errors

Similar errors include:

• CS0103: The name does not exist in the current context, often due to missing variables or typos.
• CS0120: An object reference is required for non-static members.
• CS0234: The namespace or type could not be found, usually from missing using directives.

Key Takeaways

CS1061 means you are calling a member that does not exist on the object or type.

Check spelling, member existence, and correct type usage to fix the error.

Use IDE autocomplete and proper namespaces to prevent this error.

Add missing methods or properties if they are intended to be used.

Related errors often involve missing references or incorrect context.