EF 迁移脚本在条件下退出迁移

Question

I want to abort the migration in code first approach on a condition basis.

Suppose, if the condition is true, I want to exit the migration without making changes to the database.

Answer 1

This should be possible with MigrationBuilder.Sql(String, Boolean) method, so create an SQL script with what you want to do with IF...ELSE conditions. Then create an empty migration and write the script in the Sql() method as a verbatim string.

protected override void Up(MigrationBuilder migrationBuilder)
{
    migrationBuilder.Sql(@"
    BEGIN
        DECLARE @sales INT;

        SELECT 
            @sales = SUM(list_price * quantity)
        FROM
            sales.order_items i
            INNER JOIN sales.orders o ON o.order_id = i.order_id
        WHERE
            YEAR(order_date) = 2018;

        SELECT @sales;

        IF @sales > 1000000
        BEGIN
            -- // What you want to do if sales > 1,000,000
        END
    END
    ");
}

protected override void Down(MigrationBuilder migrationBuilder)
{
    // But you need to write another script to revert the changes done by Up method.
}

If you don't know how to create a script for your migration, use Script-Migration .

I don't think you can run queries or inject services to migrations, since the Entity-framework command-line tool analyzes your code but does not run the startup.cs class.