What does expressionStack_xx_x mean?
===

I just decompiled an assembly file and noticed a lot of expressionStack_xx_x  expressions which I never encountered before. From my understanding, the compiler replaces variables with this expression but I am not certain. What are they used for and are they generated by the compiler? Incomplete example of code below:

        public void DisplayDestinationBrowser()
    {
    System.Windows.Forms.OpenFileDialog dialog2 = new System.Windows.Forms.OpenFileDialog();
    System.Windows.Forms.OpenFileDialog expressionStack_45_1 = dialog2;
    string expressionStack_45_0 = "";
    System.Windows.Forms.OpenFileDialog expressionStack_10_2 = expressionStack_45_1;
    string expressionStack_10_1 = expressionStack_45_0;
    int expressionStack_10_0 = 0xf7b1;
    }