參數化多或查詢的WHERE子句

Question

我要參數這個在：

select * from myTable where column1='1' or TaxRateRef='18'

弄成這個樣子：

String query = "select * from myTable where "; // column1='1' or column1='18' 

var parameters = new List<SqlParameter>(); 

for(int i = 0; i < data.Rows.Count;i++) 
{ 
    blah blah blah 

    query += " Column1='@column1' or"; 

    parameters.Add(new SqlParameter("@column1", i)); 

} 

但是我得到一個異常

System.Data.SqlClient.SqlException :The variable name '@column1' has already been declared.Variable names must be unique within a query batch or stored procedure. 
Incorrect syntax near 'or'. 

Answer 1

錯誤很明顯。您在for循環中多次添加參數。您應該添加此行...

parameters.Add(new SqlParameter("@column1", i)); 

只在您的查詢一次。如果您需要在每次循環添加不同的值，只需追加迭代次數（i）參數名，以使其獨特...

query += string.Format(" Column1='@column1{0}' or", i); 
parameters.Add(new SqlParameter(string.Format("@column1{0}", i), i)); 

Answer 2

原因是因爲@column1所有附加時間。使用下面的一個

parameters.Add(new SqlParameter(string.Format("@column1{0}", i), i)); 

String query = "select * from myTable where "; // column1='1' or column1='18' 

var parameters = new List<SqlParameter>(); 

for(int i = 0; i < data.Rows.Count;i++) 
{ 
    blah blah blah 

    query += " Column1='@column1' or"; 

    parameters.Add(new SqlParameter("@column1", i)); 
    parameters.Add(new SqlParameter(string.Format("@column1{0}", i), i)); 

}