/// <summary>
/// Creates a <see cref="DbBinaryExpression"/>.
/// </summary>
/// <param name="binaryExpressionType">The <see cref="DbBinaryExpressionType"/> that specifies the type of binary expression to create.</param>
/// <param name="leftExpression">A <see cref="DbExpression"/> that represents the left operand.</param>
/// <param name="rightExpression">A <see cref="DbExpression"/> that represents the right operand.</param>
/// <returns>A <see cref="DbBinaryExpression"/> instance.</returns>
public DbBinaryExpression MakeBinary(DbBinaryExpressionType binaryExpressionType, DbExpression leftExpression, DbExpression rightExpression)
{
var binaryExpression = new DbBinaryExpression(binaryExpressionType, leftExpression, rightExpression);
return binaryExpression;
}
/// <summary>
/// Translates the <paramref name="binaryExpression"/> into a string representation.
/// </summary>
/// <param name="binaryExpression">The <see cref="DbBinaryExpression"/> to translate.</param>
/// <returns><see cref="string"/></returns>
protected override DbExpression VisitBinaryExpression(DbBinaryExpression binaryExpression)
{
var body = "({0}{1}{2})";
if (binaryExpression.BinaryExpressionType == DbBinaryExpressionType.Assignment)
{
body = "{0} = {1}";
return
ExpressionFactory.Sql(string.Format(body, Visit(binaryExpression.LeftExpression),
Visit(binaryExpression.RightExpression)));
}
var leftExpression = Visit(binaryExpression.LeftExpression);
var rightExpression = Visit(binaryExpression.RightExpression);
if (binaryExpression.RightExpression.ExpressionType == DbExpressionType.Constant && ((DbConstantExpression)binaryExpression.RightExpression).Value == null)
{
if (binaryExpression.BinaryExpressionType == DbBinaryExpressionType.Equal)
return ExpressionFactory.Sql(string.Format("({0} IS {1})", leftExpression, rightExpression));
if (binaryExpression.BinaryExpressionType == DbBinaryExpressionType.NotEqual)
return ExpressionFactory.Sql(string.Format("({0} IS NOT {1})", leftExpression, rightExpression));
}
if (binaryExpression.LeftExpression.ExpressionType == DbExpressionType.Constant && ((DbConstantExpression)binaryExpression.LeftExpression).Value == null)
{
if (binaryExpression.BinaryExpressionType == DbBinaryExpressionType.Equal)
return ExpressionFactory.Sql(string.Format("({0} IS {1})", rightExpression, leftExpression));
if (binaryExpression.BinaryExpressionType == DbBinaryExpressionType.NotEqual)
return ExpressionFactory.Sql(string.Format("({0} IS NOT {1})", rightExpression, leftExpression));
}
var sqlFragment = string.Format(body, leftExpression,
GetBinaryOperator(binaryExpression.BinaryExpressionType),
rightExpression);
return ExpressionFactory.Sql(sqlFragment);
}
/// <summary>
/// Translates the <paramref name="binaryExpression"/> into a string representation.
/// </summary>
/// <param name="binaryExpression">The <see cref="DbBinaryExpression"/> to translate.</param>
/// <returns><see cref="DbExpression"/></returns>
protected virtual DbExpression VisitBinaryExpression(DbBinaryExpression binaryExpression)
{
var leftExpression = Visit(binaryExpression.LeftExpression);
var rightExpression = Visit(binaryExpression.RightExpression);
if (!leftExpression.Equals(binaryExpression.LeftExpression) ||
rightExpression.Equals(binaryExpression.RightExpression))
{
return ExpressionFactory.MakeBinary(binaryExpression.BinaryExpressionType, leftExpression, rightExpression);
}
return binaryExpression;
}
