Parameters.Add（）不涉及查詢的情況下，工作在C＃「是否存在」語句

Question

請看看下面的代碼

string SearchQuery = @"if exists (select * from table where colName = @colNameVal) select 1 else select 0"; 
AseConnection connection = new AseConnection(); 
connection.ConnectionString = connectionString; 
connection.Open(); 
try 
{ 
    AseCommand selectCommand = new AseCommand(SearchQuery, connection); 
    selectCommand.Parameters.Add(new AseParameter("@colNameVal", AseDbType.NVarChar, 13)).Value = "123"; 
    int doesValExist = (int)selectCommand.ExecuteScalar(); 
} 
catch(Exception ex) 
{ 

} 

我使用Sybase.AdoNet4.AseClient。上面的代碼拋出AseException與以下消息

「必須聲明變量'@colNameVal'」。

但以下查詢正在工作select * from table where colName = @colNameVal。

所以我假設在if exists語句的情況下添加參數會有一些問題。是否有任何解決方法來傳遞參數？

Answer 1

string SearchQuery = @"select count(*) from table where colName = @colNameVal"; 
AseConnection connection = new AseConnection(); 
connection.ConnectionString = connectionString; 
connection.Open(); 
try 
{ 
    AseCommand selectCommand = new AseCommand(SearchQuery, connection); 
    selectCommand.Parameters.Add(new AseParameter("@colNameVal", AseDbType.NVarChar, 13)).Value = "123"; 
    int doesValExist = (int)selectCommand.ExecuteScalar(); 
} 
catch(Exception ex) 
{ 

}