/// <summary>
/// Returns compiled lambda expression for given expression
/// </summary>
/// <typeparam name="T1">Input type on which to apply expression</typeparam>
/// <typeparam name="T2">Return type for the expression</typeparam>
/// <param name="exString">expression formula</param>
/// <returns>Compiled lambda expression</returns>
public static Func <T1, T2> CompileExpression <T1, T2>(ExpressionString exString)
{
var param = Expression.Parameter(typeof(T1));
var expr = BuildExpression <T1>(exString, param);
return(Expression.Lambda <Func <T1, T2> >(expr, param).Compile());
}
/// <summary>
/// Build and returns binary expression based on given expression formula
/// </summary>
/// <typeparam name="T">Type of expression to return</typeparam>
/// <param name="exString">expression formula</param>
/// <param name="param">Type used to identify operand in the expression</param>
/// <returns>Returns binary expression based on given formula</returns>
public static Expression BuildExpression <T>(ExpressionString exString, ParameterExpression param)
{
var left = MemberExpression.Property(param, exString.LeftSide);
var leftPropType = typeof(T).GetProperty(exString.LeftSide).PropertyType;
ExpressionType exprBinary;
if (ExpressionType.TryParse(exString.Operator, out exprBinary))
{
var right = Expression.Constant(Convert.ChangeType(exString.RightSide, leftPropType));
return(Expression.MakeBinary(exprBinary, left, right));
}
else
{
throw new Exception("Invalid Expression");
}
}
