Examples of errors detected by the V3156 diagnostic

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

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;

}

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;
}

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;
    }

  ....
}