EFCore CodeFirst模型迁移生成数据库备注（mysql）

重写Mysql下sql脚本生成器

using Framework.NetCore.Extensions;
using Framework.NetCore.Models;
using Microsoft.EntityFrameworkCore.Metadata;
using Microsoft.EntityFrameworkCore.Migrations;
using Microsoft.EntityFrameworkCore.Migrations.Operations;
using Pomelo.EntityFrameworkCore.MySql.Infrastructure.Internal;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;

namespace Framework.NetCore.EfDbContext
{

    public class MyMigrationsSqlGenerator : MySqlMigrationsSqlGenerator
    {
        public MyMigrationsSqlGenerator(
            MigrationsSqlGeneratorDependencies dependencies,
            IMigrationsAnnotationProvider migrationsAnnotations,
            IMySqlOptions mySqlOptions)
            : base(dependencies, migrationsAnnotations, mySqlOptions)
        {
        }

        protected override void Generate(MigrationOperation operation, IModel model, MigrationCommandListBuilder builder)
        {
            base.Generate(operation, model, builder);

            if (operation is CreateTableOperation || operation is AlterTableOperation)
                CreateTableComment(operation, model, builder);

            if (operation is AddColumnOperation || operation is AlterColumnOperation)
                CreateColumnComment(operation, model, builder);
        }

        /// <summary>
        /// Create table comment.
        /// </summary>
        /// <param name="operation"></param>
        /// <param name="builder"></param>
        private void CreateTableComment(MigrationOperation operation, IModel model, MigrationCommandListBuilder builder)
        {
            string tableName = string.Empty;
            string description = string.Empty;
            if (operation is AlterTableOperation)
            {
                var t = operation as AlterColumnOperation;
                tableName = (operation as AlterTableOperation).Name;
            }

            if (operation is CreateTableOperation)
            {
                var t = operation as CreateTableOperation;
                var addColumnsOperation = t.Columns;
                tableName = (operation as CreateTableOperation).Name;

                foreach (var item in addColumnsOperation)
                {
                    CreateColumnComment(item, model, builder);
                }
            }
            description = DbDescriptionHelper.GetDescription(tableName);

            if (tableName.IsNullOrWhiteSpace())
                throw new Exception("Create table comment error.");

            var sqlHelper = Dependencies.SqlGenerationHelper;
            builder
            .Append("ALTER TABLE ")
            .Append(sqlHelper.DelimitIdentifier(tableName).ToLower())
            .Append(" COMMENT ")
            .Append("'")
            .Append(description)
            .Append("'")
            .AppendLine(sqlHelper.StatementTerminator)
            .EndCommand();

        }

        /// <summary>
        /// Create column comment.
        /// </summary>
        /// <param name="operation"></param>
        /// <param name="builder"></param>
        private void CreateColumnComment(MigrationOperation operation, IModel model, MigrationCommandListBuilder builder)
        {
            //alter table a1log modify column UUID VARCHAR(26) comment '修改后的字段注释';
            string tableName = string.Empty;
            string columnName = string.Empty;
            string columnType = string.Empty;
            string description = string.Empty;
            if (operation is AlterColumnOperation)
            {
                var t = (operation as AlterColumnOperation);
                tableName = t.Table;
                columnName = t.Name;
                columnType = GetColumnType(t.Schema, t.Table, t.Name, t.ClrType, t.IsUnicode, t.MaxLength, t.IsFixedLength, t.IsRowVersion, model);
            }

            if (operation is AddColumnOperation)
            {
                var t = (operation as AddColumnOperation);
                tableName = t.Table;
                columnName = t.Name;
                columnType = GetColumnType(t.Schema, t.Table, t.Name, t.ClrType, t.IsUnicode, t.MaxLength, t.IsFixedLength, t.IsRowVersion, model);
                description = DbDescriptionHelper.GetDescription(tableName, columnName);
            }

            if (columnName.IsNullOrWhiteSpace() || tableName.IsNullOrWhiteSpace() || columnType.IsNullOrWhiteSpace())
                throw new Exception("Create columnt comment error." + columnName + "/" + tableName + "/" + columnType);

            var sqlHelper = Dependencies.SqlGenerationHelper;
            builder
            .Append("ALTER TABLE ")
            .Append(sqlHelper.DelimitIdentifier(tableName).ToLower())
            .Append(" MODIFY COLUMN ")
            .Append(columnName)
            .Append(" ")
            .Append(columnType)
            .Append(" COMMENT ")
            .Append("'")
            .Append(description)
            .Append("'")
            .AppendLine(sqlHelper.StatementTerminator)
            .EndCommand();

        }
    }

    public class DbDescriptionHelper
    {
        public static string b { get; set; } = "Framework.Website.Models";
        public static string c { get; set; } = @"C:\Users\fxy75\Downloads\pos3.0\Framework.Website.Models";

        public static List<DbDescription> list { get; set; }

        public static string GetDescription(string table, string column = "")
        {
            if (list == null || list.Count() == 0)
            {
                list = GetDescription();
            }

            if (!string.IsNullOrWhiteSpace(table))
            {
                if (string.IsNullOrWhiteSpace(column))
                {
                    var x = list.FirstOrDefault(p => p.Name == table);
                    if (x != null)
                        return x.Description;
                    return string.Empty;
                }
                else
                {
                    var x = list.FirstOrDefault(p => p.Name == table);
                    if (x != null)
                    {
                        var y = x.Column;
                        if (y.IsNotNull())
                        {
                            var z = y.FirstOrDefault(p => p.Name == column);
                            if (z != null)
                                return z.Description;
                        }
                    }
                    return string.Empty;
                }
            }
            else
                return string.Empty;
        }

        public static List<DbDescription> GetDescription()
        {
            var d = new List<DbDescription>();

            var e = Assembly.Load(b);
            var f = e?.GetTypes();
            var g = f?
                .Where(t => t.IsClass
                && !t.IsGenericType
                && !t.IsAbstract
                && t.GetInterfaces().Any(m => m.GetGenericTypeDefinition() == typeof(IBaseModel<>))
                ).ToList();

            foreach (var h in g)
            {
                var i = new DbDescription();

                var j = c + "\\" + h.Name + ".cs";
                var k = File.ReadAllText(j);
                k = k.Substring(k.IndexOf("{") + 1, k.LastIndexOf("}") - k.IndexOf("{") - 1).Replace("\n", "");

                var l = k.Substring(k.IndexOf(" {") + 2, k.LastIndexOf(" }") - k.IndexOf(" {") - 1).Replace("\n", "");
                string[] slipt = { "}\r" };
                var m = l.Split(slipt, StringSplitOptions.None).ToList();

                var n = new List<DbDescription>();
                foreach (var o in m)
                {
                    var p = o.Replace("///", "");

                    var q = p.IndexOf("<summary>");
                    var r = p.LastIndexOf("</summary>");

                    var s = p.IndexOf("public");
                    var t = p.IndexOf("{");

                    var u = (q > 0 && r > 0) ? p.Substring(q + 9, r - q - 10).Replace("\r", "").Replace(" ", "") : "";
                    var v = (s > 0 && t > 0) ? p.Substring(s, t - s).Split(' ')[2] : "";

                    n.Add(new DbDescription()
                    {
                        Description = u,
                        Name = v
                    });
                }

                var w = k.Substring(0, k.IndexOf("{\r") - 1);
                w = w.Replace("///", "");

                var x = w.IndexOf("<summary>");
                var y = w.LastIndexOf("</summary>");
                var z = (x > 0 && y > 0) ? w.Substring(x + 9, y - x - 10).Replace("\r", "").Replace(" ", "") : "";

                d.Add(new DbDescription()
                {
                    Name = h.Name,
                    Description = z,
                    Column = n
                });
            }
            return d;
        }
    }

    public class DbDescription
    {
        public string Name { get; set; }
        public string Description { get; set; }
        public List<DbDescription> Column { get; set; }
    }
}

EFCore DbContext中替换IMigrationsSqlGenerator

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder
                .UseMySql(_option.ConnectionString)
                .ReplaceService<IMigrationsSqlGenerator, MyMigrationsSqlGenerator>();

            base.OnConfiguring(optionsBuilder);
        }

原文地址：https://www.cnblogs.com/fuxuyang/p/10835904.html