Custom Migration Operations shows incorrect way to get type mapping source for string

[klemmchr]

Type of issue

Code doesn't work

Description

Using a MigrationOperation shows the following code

public class MyMigrationsSqlGenerator : SqlServerMigrationsSqlGenerator
{
    public MyMigrationsSqlGenerator(
        MigrationsSqlGeneratorDependencies dependencies,
        ICommandBatchPreparer commandBatchPreparer)
        : base(dependencies, commandBatchPreparer)
    {
    }

    protected override void Generate(
        MigrationOperation operation,
        IModel model,
        MigrationCommandListBuilder builder)
    {
        if (operation is CreateUserOperation createUserOperation)
        {
            Generate(createUserOperation, builder);
        }
        else
        {
            base.Generate(operation, model, builder);
        }
    }

    private void Generate(
        CreateUserOperation operation,
        MigrationCommandListBuilder builder)
    {
        var sqlHelper = Dependencies.SqlGenerationHelper;
        var stringMapping = Dependencies.TypeMappingSource.FindMapping(typeof(string)); // <--------------------------

        builder
            .Append("CREATE USER ")
            .Append(sqlHelper.DelimitIdentifier(operation.Name))
            .Append(" WITH PASSWORD = ")
            .Append(stringMapping.GenerateSqlLiteral(operation.Password))
            .AppendLine(sqlHelper.StatementTerminator)
            .EndCommand();
    }
}

The marked line returns null.

The CLR Type mappings simply don't contain a string type key

I am unable to find the right way of getting a string type mapping.

Page URL

https://learn.microsoft.com/en-us/ef/core/managing-schemas/migrations/operations

Content source URL

https://github.com/dotnet/EntityFramework.Docs/blob/main/entity-framework/core/managing-schemas/migrations/operations.md

Document Version Independent Id

aafc9673-c635-3cf2-6235-8577ff15d19c

Article author

@bricelam