updated on Jul. 19, 2012



EvaluateExpress.dll is a dynamic-link library (DLL) to give a function to evaluate mathematical expression to your application. You can find its ability by using yoshinoCALC in History View. This DLL is completely free as long as you can use it for non-commercial purpose.


yoshinoCALC (ver. 3.0.5) installer package

VB2010 sample using EvaluateExpression.dll described below

How to

Getting EvaluateExpression.dll

  • Install yoshinoCALC to a PC.
  • Find the folder where yoshinoCALC is installed. Its default location is "c:\Program Files\yoshinoCALC". EvaluateExpress.dll is in the folder.

Creating a Microsoft Visual Studio .NET project

  • Create a new project in your favorite language such as Visual Basic and Visual C#. Here I use Microsoft Visual Basic 2005 Express Edition.

  • Add two TextBoxes and one Button to Form1.

  • Select [Project]-[Add Reference...] in the menu to add the dll to the project.

  • Find and add "EvaluateExpression.dll" in the yoshinoCALC folder using the "Browse" tab.

  • Enter the follwoing command to Form1.vb.
    1) TextBox2.Text = EvaluateExpress.Calculate.Out(TextBox1.Text.ToString(), True)
    2) TextBox2.Text = EvaluateExpress.Calculate.Out(TextBox1.Text.ToString())
    In case of 1), the first argument is a string of an math expression like "sin(pi/2)". The second argument is a bool to select the angle unit, namely, True:radian or False:degree.
    In case of 2), the angle unit is always radian.
    The dll returns the answer as a string.

  • Start debugging. The application window opens. Type an expression in TextBox1.

  • Press the Button1. The answer will appear in TextBox2.

  • If the expression you enter is inappropriate, the dll returns a string "Evaluation Impossible".

  • Please consult the manual of yoshinoCALC to find operators, functions and constants you can use.