在语句中写:例如:
myselectstr = "select xxbm,xxbt,nvl(xxcc,'') as xxcc,fbsj,nvl(xxzy,'') as xxzy,nvl(xxnr,'') as xxnr,nvl(tpxx,0) as tpxx,nvl(fjxx,0) as fjxx ,nvl(gjc,'') as gjc,nvl(xxbz,'') as xxbz,nvl(jzrq,'') as jzrq ,nvl(sfzd,0) as sfzd ,nvl(xxzz,'') as xxzz ,fwcs from esot_information where xxbm='" & _MessageId & "'"
我的是oracle库
若是sql库将nvl 该成isnull
myselectstr = "select xxbm,xxbt,nvl(xxcc,'') as xxcc,fbsj,nvl(xxzy,'') as xxzy,nvl(xxnr,'') as xxnr,nvl(tpxx,0) as tpxx,nvl(fjxx,0) as fjxx ,nvl(gjc,'') as gjc,nvl(xxbz,'') as xxbz,nvl(jzrq,'') as jzrq ,nvl(sfzd,0) as sfzd ,nvl(xxzz,'') as xxzz ,fwcs from esot_information where xxbm='" & _MessageId & "'"
我的是oracle库
若是sql库将nvl 该成isnull
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但是在C#里写的函数,要修改指向的值,也必须是REF方式啊
未处理的"System.NullReferenceException"类型的异常出现在MyApp.exe中。
其他信息:未将对象引用设置到对象的实例。
若要使用 ref 参数,必须将参数作为 ref 参数显式传递到方法。ref 参数的值被传递到 ref 参数。
传递到 ref 参数的参数必须最先初始化。将此方法与 out 参数相比,后者的参数在传递到 out 参数之前不必显式初始化。
属性不是变量,不能作为 ref 参数传递。
如果两种方法的声明仅在它们对 ref 的使用方面不同,则将出现重载。但是,无法定义仅在 ref 和 out 方面不同的重载。例如,以下重载声明是有效的:
class MyClass
{
public void MyMethod(int i) {i = 10;}
public void MyMethod(ref int i) {i = 10;}
}
但以下重载声明是无效的:
class MyClass
{
public void MyMethod(out int i) {i = 10;}
public void MyMethod(ref int i) {i = 10;}
}
有关传递数组的信息,请参见使用 ref 和 out 传递数组。
示例
// cs_ref.cs
using System;
public class MyClass
{
public static void TestRef(ref char i)
{
// The value of i will be changed in the calling method
i = 'b';
} public static void TestNoRef(char i)
{
// The value of i will be unchanged in the calling method
i = 'c';
} // This method passes a variable as a ref parameter; the value of the
// variable is changed after control passes back to this method.
// The same variable is passed as a value parameter; the value of the
// variable is unchanged after control is passed back to this method.
public static void Main()
{
char i = 'a'; // variable must be initialized
TestRef(ref i); // the arg must be passed as ref
Console.WriteLine(i);
TestNoRef(i);
Console.WriteLine(i);
}
}
输出
b
b