传入模型时如何使用 Dapper 构建动态 Where 子句

Question

我有一个示例模型，如下所示：

public class PersonModel
{
     public int Id {get; set;}
     public string FirstName {get; set;}
     public string Lastname {get; set;}
     public string City {get; set;}
}

在我的存储库中，我想创建一个在我的模型中传递的搜索方法 - 但并非所有字段都将始终被填充。我想根据模型中的字段是否已填充来创建 WHERE 和 AND。如果该字段未填充，那么我不想为其创建 WHERE 子句。

例如 - 如果我传入 FirstName = "Bob" 和 City = "Boston" 那么我希望我的搜索看起来像这样：

SELECT * FROM PersonTable WHERE FirstName = @firstName AND City = @city

因为我没有传入 Id 或 LastName，所以我不想将它们添加到查询中。如果我只是通过 City = "Boston" 那么我希望它看起来像这样：

SELECT * FROM PersonTable WHERE City = @city

我的回购方法看起来像这样

using Dapper;
public List<PersonModel> Search(PersonModel model)
{
//db = DbConnection connection
    var selectSql = "SELECT * FROM PersonTable "; //build out where clause somehow
    return db.Query<PersonModel>(selectSql).ToList();
}

我的问题是如何在我的回购方法中正确构建它？

Answer 1

bool isFirstWhereSet = false;
bool isCityWhereSet = false;
string sqlQuery = "SELECT * FROM PersonTable "  ;
if (! String.IsNullOrEmpty(model.FirstName ))
{
sqlQuery  =sqlQuery  + "WHERE FirstName =@FirstName" ;
isFirstWhereSet = true;
}

if (! String.IsNullOrEmpty(model.City))
{
isCityWhereSet  = true ;
if (! isFirstWhereSet )
sqlQuery  = sqlQuery  + " WHERE City = @city";
else
sqlQuery  = sqlQuery  + " AND City = @city";
}



if (isFirstWhereSet == true && isCityWhereSet == true )
 return db.Query<PersonModel>(sqlQuery , new { FirstName = model.FirstName  , City = mode.City}).ToList();
else if (isFirstWhereSet == true && isCityWhereSet  == false)
 return db.Query<PersonModel>(sqlQuery , new { FirstName = model.FirstName }).ToList();
else if (isFirstWhereSet == false && isCityWhereSet  == true)
 return db.Query<PersonModel>(sqlQuery , new { City= model.City}).ToList();
else
{
 return db.Query<PersonModel>(sqlQuery).ToList();
}

Answer 2

这应该可以为您解决问题，简洁明了：

var selectSql = "SELECT * FROM PersonTable WHERE (@FirstName IS NULL OR FirstName =  @FirstName) AND (@LastName IS NULL OR LastName =  @LastName) AND (@City IS NULL OR City =  @City) AND (@Id IS NULL OR Id =  @Id) OPTION(RECOMPILE)";

return conn.Query<PersonModel>(selectSql, new
{
     model.FirstName,
     model.Lastname,
     model.City,
     Id = model.Id == 0? (int?)null: (int?)model.Id        
}).ToList();

Answer 3

您也可以使用 Dapper 的 SqlBuilder。

请注意，您必须安装 Dapper.SqlBuilder NuGet 包，因为它没有随 Dapper 的主要发行版一起提供。

这是一个例子：

    [Test]
    public void Test()
    {
        var model = new PersonModel {FirstName = "Bar", City = "New York"};

        var builder = new SqlBuilder();

        //note the 'where' in-line comment is required, it is a replacement token
        var selector = builder.AddTemplate("select * from table /**where**/");

        if (model.Id > 0)
            builder.Where("Id = @Id", new { model.Id });

        if (!string.IsNullOrEmpty(model.FirstName))
            builder.Where("FirstName = @FirstName", new { model.FirstName });

        if (!string.IsNullOrEmpty(model.Lastname))
            builder.Where("Lastname = @Lastname", new { model.Lastname });

        if (!string.IsNullOrEmpty(model.City))
            builder.Where("City = @City", new { model.City });

        Assert.That(selector.RawSql, Is.EqualTo("select * from table WHERE FirstName = @FirstName AND City = @City\n"));

        //var rows = sqlConnection.Query(selector.RawSql, selector.Parameters);
    }

您可以找到一些示例 here。

Answer 4

您可以使用 ExpressionExtensionSQL 库。此库将 lambda 表达式转换为 where 子句，并可与 dapper 和 ADO 一起使用。

Answer 5

如果您想尝试其他选择，DapperQueryBuilder 可能更容易使用：

var query = cn.QueryBuilder($@"
    SELECT * 
    FROM PersonTable
   /**where**/
");

if (model.Id > 0)
    query.Where($"Id = {model.Id}");

if (!string.IsNullOrEmpty(model.FirstName))
    query.Where($"FirstName = {model.FirstName}");

if (!string.IsNullOrEmpty(model.Lastname))
    query.Where($"Lastname = {model.Lastname}");

if (!string.IsNullOrEmpty(model.City))
    query.Where($"City = {model.City}");


var results = query.Query<Person>();

Query<Person>() 将调用传递底层 SQL 和参数的 Dapper。

底层查询已完全参数化SQL:
WHERE FirstName = @p0 AND LastName = @p1,等等

或者，更简单：

var query = cn.QueryBuilder($"SELECT * FROM PersonTable WHERE 1=1");

if (model.Id > 0) 
    query += $"AND Id = {model.Id}";

if (!string.IsNullOrEmpty(model.FirstName))
    query += $"AND FirstName = {model.FirstName}";

if (!string.IsNullOrEmpty(model.Lastname))
    query += $"AND Lastname = {model.Lastname}";

if (!string.IsNullOrEmpty(model.City))
    query += $"AND City = {model.City}";


var results = query.Query<Person>();

免责声明：我是该库的作者之一

传入模型时如何使用 Dapper 构建动态 Where 子句

How do I build a dynamic Where clause with Dapper when passing in a model

.net

c#

sql

dapper