How to deal with Code Contracts warning CC1036 when using string.IsNullOrWhiteSpace?

Question

I have the following code contract:

public void F(string x) {     Contract.Requires(!string.IsNullOrWhiteSpace(x));      throw new NotImplementedException(); } 

When compiling, I get the following warning:

warning CC1036: Detected call to method 'System.String.IsNullOrWhiteSpace(System.String)' without [Pure] in contracts of method [...]

How to deal with it?

What's odd, is that I'm also using string.IsNullOrEmpty, which isn't marked as [Pure] as well, in other contracts and the rewriter does not have a problem with that.

My Contract Rewriter's Version is 1.9.10714.2.

This is the relevant part from the implementation of String class I'm using (retrieved from metadata):

#region Assembly mscorlib.dll, v4.0.0.0 // C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\mscorlib.dll #endregion  using System.Collections; using System.Collections.Generic; using System.Globalization; using System.Reflection; using System.Runtime.ConstrainedExecution; using System.Runtime.InteropServices; using System.Security; using System.Text;  namespace System {     // Summary:     //     Represents text as a series of Unicode characters.To browse the .NET Framework     //     source code for this type, see the Reference Source.     [Serializable]     [ComVisible(true)]     public sealed class String : IComparable, ICloneable, IConvertible, IEnumerable, IComparable<string>, IEnumerable<char>, IEquatable<string>     {      // [...]          //         // Summary:         // [...]         public static bool IsNullOrEmpty(string value);         //         // Summary:         // [...]         public static bool IsNullOrWhiteSpace(string value); 

Why is the [Pure] attribute missing?

Answer 1

Here we have two points:

1. Why is the [Pure] attribute missing in string class for IsNullorWhiteSpace function?

2. How to resolve the CC1030 warning issue?

I will try to discuss both.

1. Why is the [Pure] attribute missing? It's not missing, metadata does not seem to be showing this.

This may not be marked as Pure in previous version of .NET FX as, they were saying:

Yes, we need to make our checker sensitive to the disable pragma...

Sigh.

We currently don't have that implemented, but I've added it to our work list.

Refer to the 5 year old discussion here.

But this has been marked as Pure in latest FX (4.6.1), Refer to .NET Framework 4.6.1, the new string class code.

[Pure] public static bool IsNullOrWhiteSpace(String value) {     if (value == null) return true;      for(int i = 0; i < value.Length; i++) {         if(!Char.IsWhiteSpace(value[i])) return false;     }      return true; } 

Then Why CC1036?

This warning "CC1036" is from CodeContracts, developers have open this issue yesterday only (refer here).

Now why metadata is not spitting up Pure attributes, this is a different question, like for Equals method, Pure is added but only SecuritySafeCritical is displayed in metadata code.

[SecuritySafeCritical] public static bool Equals(String a, String b, StringComparison comparisonType); 

The same problem applies to Invariant(). Given the following code, the same warnings are displayed:

private string testString = "test";  [ContractInvariantMethod] private void TestInvariant() {      Contract.Invariant(!string.IsNullOrWhiteSpace(testString)); } 

How to resolve?

As others are also suggesting, create another method, mark it as Pure and call this in your contract condition.