workgroupengineering/dynamicexpressionbuilder

C# expression builder at run-time.

Overview

Simple C# expression builder at run-time. Currently supports these operations:

public enum Operation
    {
        Equals,
        NotEquals,
        GreaterThan,
        LessThan,
        GreaterThanOrEqual,
        LessThanOrEqual,
        Contains,
        ContainsWithToLower,
        ToStringWithContains,
        StartsWith,
        EndsWith,
        StartsWithToLower,
        EndsWithToLower,
        StringEquals
    }

Implementation

Steps:

• Build expression input list

public static IList<ExpressionInput> GetExpressionInputList()
        {
            return new List<ExpressionInput>
            {
                new ExpressionInput
                {
                    Operand = Operand.And, //First Item does not matter And or OR
                    Operation = Operation.Contains,
                    PropertyName = "Name",
                    Value = "Jack"
                },
                new ExpressionInput
                {
                    Operand = Operand.And,
                    Operation = Operation.Equals,
                    PropertyName = "Id",
                    Value = 1
                },
                new ExpressionInput
                {
                    Operand = Operand.And,
                    Operation = Operation.Equals,
                    PropertyName = "State",
                    Value = "FL"
                },
                new ExpressionInput
                {
                    Operand = Operand.Or,
                    Operation = Operation.Equals,
                    PropertyName = "CrimeRecord",
                    Value = false
                },
                new ExpressionInput
                {
                    Operand = Operand.And,
                    Operation = Operation.Equals,
                    PropertyName = "AnnualIncome",
                    Value = (long)50000 //Value need to be parsed to Expression's object (T) type. Here T is of Citizen type and AnnualIncome is of double type.
                }
            };
        }

• Passed to ExpressionBuilder

            var expressionList = ExpressionInputGenerator.GetExpressionInputList();

            var expression = DynamicExpressionBuilder.ExpressionBuilder.GetExpression<Citizen>(expressionList); //Passing to expression builder. Here we are getting expression of Type Citizen
            Console.WriteLine($"Final Expression = {expression.ToString()}");

Output: Final Expression = t => ((((t.Name.Contains("Jack") AndAlso t.Id.Equals(1)) AndAlso t.State.Equals("FL")) Or t.CrimeRecord.Equals(False)) AndAlso t.AnnualIncome.Equals(50000))

• Using Final expression

            var citizenRecords = CitizenRecordGenerator.GetCitizenRecordList();
            var expression = DynamicExpressionBuilder.ExpressionBuilder.GetExpression<Citizen>(expressionList)

            var filterCitizens = citizenRecords.Where(expression.Compile()); //Expression Implementation
            Console.WriteLine($"\nFilter records: {filterCitizens.Count()}");

Conclusion

Above code are from example console app which is inside project.