NullIfTranslator.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using Microsoft.EntityFrameworkCore.Query.SqlExpressions;

namespace Microsoft.EntityFrameworkCore.Query.Internal;

/// <summary>
///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
///     the same compatibility standards as public APIs. It may be changed or removed without notice in
///     any release. You should only use it directly in your code with extreme caution and knowing that
///     doing so can result in application failures when updating to a new Entity Framework Core release.
/// </summary>
public class NullIfTranslator : IMethodCallTranslator
{
    private static readonly MethodInfo MethodInfo
        = typeof(RelationalDbFunctionsExtensions).GetMethod(nameof(RelationalDbFunctionsExtensions.NullIf))!;

    private readonly ISqlExpressionFactory _sqlExpressionFactory;

    /// <summary>
    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
    ///     any release. You should only use it directly in your code with extreme caution and knowing that
    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
    /// </summary>
    public NullIfTranslator(ISqlExpressionFactory sqlExpressionFactory)
    {
        _sqlExpressionFactory = sqlExpressionFactory;
    }

    /// <summary>
    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
    ///     any release. You should only use it directly in your code with extreme caution and knowing that
    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
    /// </summary>
    public SqlExpression? Translate(
        SqlExpression? instance,
        MethodInfo method,
        IReadOnlyList<SqlExpression> arguments,
        IDiagnosticsLogger<DbLoggerCategory.Query> logger)
        => method.IsGenericMethod
            && Equals(method.GetGenericMethodDefinition(), MethodInfo)
                ? _sqlExpressionFactory.Function(
                    "NULLIF",
                    new[] { arguments[1], arguments[2] },
                    nullable: true,
                    argumentsPropagateNullability: new[] { true, true },
                    method.ReturnType)
                : null;
}