Multiple Conditions in Lambda Expressions at runtime C#

Posted by Ryan on Stack Overflow See other posts from Stack Overflow or by Ryan
Published on 2010-03-21T11:30:59Z Indexed on 2010/03/21 12:21 UTC
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Hi,

I would like to know how to be able to make an Expression tree by inputting more than one parameter

Example:

dataContext.Users.Where(u => u.username == "Username" && u.password == "Password")

At the moment the code that I did was the following but would like to make more general in regards whether the condition is OR or AND

public Func<TLinqEntity, bool> ANDOnlyParams(string[] paramNames, object[] values)
    {
        List<ParameterExpression> paramList = new List<ParameterExpression>();
        foreach (string param in paramNames)
        {
            paramList.Add(Expression.Parameter(typeof(TLinqEntity), param));
        }

        List<LambdaExpression> lexList = new List<LambdaExpression>();
        for (int i = 0; i < paramNames.Length; i++)
        {
            if (i == 0)
            {
                Expression bodyInner = Expression.Equal(
                                    Expression.Property(
                                        paramList[i], paramNames[i]),
                                        Expression.Constant(values[i]));
                lexList.Add(Expression.Lambda(bodyInner, paramList[i]));
            }
            else
            {
                Expression bodyOuter = Expression.And(
                                    Expression.Equal(
                                    Expression.Property(
                                    paramList[i], paramNames[i]),
                                    Expression.Constant(values[i])),
                                    Expression.Invoke(lexList[i - 1], paramList[i]));
                lexList.Add(Expression.Lambda(bodyOuter, paramList[i]));
            }
        }

        return ((Expression<Func<TLinqEntity, bool>>)lexList[lexList.Count - 1]).Compile();
    }

Thanks

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