无法在我的课程中使用pictureBox.Image

Question

I am making a game and I have a class called gameScripts . Inside gameScripts is a public void method called paintSquare . When this method is called,the method uses 2 if statements,and depending on which one is true,the squares image will be changed accordingly.

The problem is,when I try to use pictureBox.Image = Image.FromFile("cross.png"); to change the picture to a cross, pictureBox.Image gets a red line under it with the error message " Error 2 'System.Windows.Forms.Control' does not contain a definition for 'Image' and no extension method 'Image' accepting a first argument of type 'System.Windows.Forms.Control' could be found (are you missing a using directive or an assembly reference?) c:\\x\\x\\x\\x\\x\\x\\x\\gameScripts.cs "

I have tried including System.Drawing and System.Windows.Forms in my namespaces,but I still get this error.

Any help would be appreciated,thanks.

Answer 1

The message 'ClassXXX' does not contain a definition for 'YYY' and no extension method 'YYY' accepting a first argument of type 'ClassXXX' could be found (are you missing a using directive or an assembly reference?) means literally what it says. Most likely in you code there is construction like this:

myObject.YYY

but the class, the instance of which the myObject is, does not have a member with name YYY.

For example:

class MyClass {
     public string MyField;
}

...

var myObj = new MyClass();
myObj.MyField = "OK";
myObj.NotMyField = "FAIL"; // compiler will complain at this line

However, the compiler gets the list of available properties and methods by looking at the variable type. This may lead to the situation when the object itself have the member but compiler cannot see it as the variable is defined with a different type.

Consider the following code fragment:

class MyExtClass : MyClass {
     public string MyNewField;
}

...

MyClass myObj = new MyExtClass();
myObj.MyField = "OK";
myObj.MyNewField = "FAIL"; // compiler will complain at this line
                           // because MyClass does not have it

So in your code the pictureBox is seems to be defined as System.Windows.Forms.Control . So even if it is, in fact, System.Windows.Forms.PictureBox , compiler cannot know it and stops with the error.