FormattableSb

A mutable FormattableString class:

List<DateTime> summerDates = GetSummerDates();

FormattableStringBuilder sqlBuilder = new FormattableStringBuilder()
    .AppendInterpolated($"INSERT INTO dbo.VacationDates (Date)")
    .AppendLine()
    .AppendInterpolated($"VALUES ");

for (int i = 0; i < summerDates.Count; i++)
{
    if (i > 0)
    {
        sqlBuilder
            .AppendInterpolated($",")
            .AppendLine();
    }

    sqlBuilder.AppendInterpolated($"({summerDates[i]})");
}

FormattableString sql = sqlBuilder.ToFormattableString();
// sql.Format:
// INSERT INTO dbo.VacationDates (Date)
// VALUES ({0}),
// ({1}),
// ({2}),
// ...

// sql.GetArguments():
// [
//   System.DateTime,
//   System.DateTime,
//   System.DateTime,
//   ...
// ]

static List<DateTime> GetSummerDates()
{
    DateTime startDate = new(2040, 6, 20);
    DateTime endDate = new(2040, 9, 22);

    List<DateTime> dates = new();

    for (DateTime date = startDate; date <= endDate; date = date.AddDays(1))
    {
        dates.Add(date);
    }

    return dates;
}

With EF Core:

using VacationingContext context = new();
int rowsAffected = context.Database.ExecuteSql(sql);
// dbug: 6/19/2040 15:59:59.999 RelationalEventId.CommandExecuting[20100] (Microsoft.EntityFrameworkCore.Database.Command)
//       Executing DbCommand [Parameters=[@p0='?' (DbType = DateTime2), @p1='?' (DbType = DateTime2), @p2='?' (DbType = DateTime2), ...], CommandType='Text', CommandTimeout='30']
//       INSERT INTO dbo.VacationDates (Date)
//       VALUES (@p0),
//       (@p1),
//       (@p2),
//       ....

Features:

• Adheres to the C# language specification
• Can be used when you want to modify a FormattableString
• Preserves alignment and format strings

API:

AppendInterpolated:

/// <summary>
/// Appends the specified interpolated string to the end of the composite format string,
/// replacing its arguments with placeholders and adding them as objects.
/// </summary>
/// <param name="handler">The interpolated string to append, along with the arguments.</param>
/// <returns>A reference to this instance after the append operation has completed.</returns>
public FormattableStringBuilder AppendInterpolated([InterpolatedStringHandlerArgument("")] ref AppendInterpolatedHandler handler)

AppendLine:

/// <summary>
/// Appends the default line terminator to the end of the composite format string.
/// </summary>
/// <returns>A reference to this instance after the append operation has completed.</returns>
public FormattableStringBuilder AppendLine()

ToFormattableString:

/// <summary>
/// Creates a <see cref="FormattableString"/> from this builder.
/// </summary>
/// <returns>The object that represents the composite format string and its arguments.</returns>
public FormattableString ToFormattableString()

Setup:

• Install FormattableSb via NuGet Package Manager, Package Manager Console or dotnet CLI:

Install-Package FormattableSb

dotnet add package FormattableSb

Credits:

• Thanks to Stephen Toub for the implementation