Case Sensitivity

Functions and Parameters

By default, the evaluation process is case-sensitive. This means every parameter and function evaluation will match with case sensitivity. This behavior can be overriden for both using an IDictionary implementation with a custom StringComparer.

Also, when lowercase lookup of identifiers is enabled using the LowerCaseIdentifierLookup flag in ExpressionOptions, the evaluation engine looks for parameters and functions by first converting the identifier to all lowercase. This approach enables one to implement the case-insensitive mode by populating those dictionaries with all lowercase names.

Case-insensitive function

var expression = new Expression("secretOperation()")
{
    Functions = new Dictionary<string, ExpressionFunction>(StringComparer.InvariantCultureIgnoreCase)
    {
        { "SecretOperation", (arguments) => 42 }
    }
};

Case-insensitive parameter

var expression = new Expression("name == 'Beatriz'")
{
    Parameters = new Dictionary<string, object>(StringComparer.InvariantCultureIgnoreCase)
    {
        { "Name", "Beatriz" }
    }
};

Case-insensitive built-in function

var expression = new Expression("aBs(-1)", ExpressionOptions.IgnoreCaseAtBuiltInFunctions);

String Comparison

You can also change the comparison of string values using CaseInsensitiveStringComparer.

var expression = new Expression("{PageState} == 'list'");
expression.Parameters["PageState"] = "List";
Debug.Assert(false, expression.Evaluate());

expression = new Expression("{PageState} == 'list'", ExpressionOptions.CaseInsensitiveStringComparer);
expression.Parameters["PageState"] = "List";
Debug.Assert(true, expression.Evaluate());