编写前置和后置条件的连贯接口库:CuttingEdge.Conditions

public ICollection GetData(Nullable<int> id, string xml, ICollection col)   
{    
    // Check all preconditions:    
    Condition.Requires(id, "id")    
        .IsNotNull()          // throws ArgumentNullException on failure    
        .IsInRange(1, 999)    // ArgumentOutOfRangeException on failure    
        .IsNotEqualTo(128);   // throws ArgumentException on failure    
    Condition.Requires(xml, "xml")    
        .StartsWith("<data>") // throws ArgumentException on failure    
        .EndsWith("</data>"); // throws ArgumentException on failure    
    Condition.Requires(col, "col")    
        .IsNotNull()          // throws ArgumentNullException on failure    
        .IsEmpty();           // throws ArgumentException on failure    
    // Do some work 
    // Example: Call a method that should not return null   
    object result = BuildResults(xml, col);    
    // Check all postconditions:    
    Condition.Ensures(result, "result")    
        .IsOfType(typeof(ICollection)); // throws PostconditionException on failure    
    return (ICollection)result;    
}

 
public static int[] Multiply(int[] left, int[] right)    
{    
    Condition.Requires(left, "left").IsNotNull();    
    // You can add an optional description to each check    
    Condition.Requires(right, "right")    
        .IsNotNull()    
        .HasLength(left.Length, "left and right should have the same length");    
    // Do multiplication    
}