Examples of errors detected by the V3156 diagnostic

V3156. The argument of the method is not expected to be null.

TowerDefense-GameFramework-Demo

V3156 The first argument of the 'Add' method is not expected to be null. FileSystem.cs 206

public static FileSystem Load(....)
{
  ....

  for (int i = 0; i < fileSystem.m_BlockDatas.Count; i++)
  {
    BlockData blockData = fileSystem.m_BlockDatas[i];
    if (blockData.Using)
    {
      StringData stringData = fileSystem.ReadStringData(blockData.StringIndex);
      fileSystem.m_StringDatas.Add(blockData.StringIndex, stringData);
      fileSystem.m_FileDatas.Add(stringData.GetString(....);          // <=
    }
    else
    {
      fileSystem.m_FreeBlockIndexes.Add(blockData.Length, i);
    }
  }

  return fileSystem;
}

public string GetString(byte[] encryptBytes)
{
    if (m_Length <= 0)
    {
        return null;
    }

  ....
}

Cloudscribe

V3156 The first argument of the 'AddLoginAsync' method is not expected to be null. Potential null value: user as TUser. SiteUserManager.cs 257

public async Task<IdentityResult> TryCreateAccountForExternalUser(....)
{
  ....

  var user = new SiteUser
  {
    SiteId = Site.Id,
    UserName = userName,
    Email = email,
    FirstName = info.Principal.FindFirstValue(ClaimTypes.GivenName),
    LastName = info.Principal.FindFirstValue(ClaimTypes.Surname),
    AccountApproved = Site.RequireApprovalBeforeLogin ? false : true
  };

  user.DisplayName = _displayNameResolver.ResolveDisplayName(user);

  var result = await CreateAsync(user as TUser);
  if(result.Succeeded)
  {
    result = await AddLoginAsync(user as TUser, info);
  }

  return result;
}

MonoGame

V3156 The first argument of the 'Add' method is not expected to be null. Potential null value: sampler.Name. MonoGame.Effect.Compiler ParseTree.cs 1111

protected virtual object EvalSampler_Declaration(....)
{
  if (this.GetValue(tree, TokenType.Semicolon, 0) == null)
    return null;

  var sampler = new SamplerStateInfo();
  sampler.Name = this.GetValue(tree, TokenType.Identifier, 0) as string;
  foreach (ParseNode node in Nodes)
    node.Eval(tree, sampler);

  var shaderInfo = paramlist[0] as ShaderInfo;
  shaderInfo.SamplerStates.Add(sampler.Name, sampler);    // <=

  return null;

}