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Muhu
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ERROR: You can only take the address of an unfixed expression inside of a fixed statement initializer

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Hello
I wrote the following code, and got an error:

unsafe void Get_ADC_Samples_From_All_Enabled_Channels(TextBox tb_OutputNumber_ADC, TextBox tb_Voltage_ADC)
{

bool got;

double[,] channelData = new double[64,8];
double*[] voltagePointerArray = new double*[64];

for (int i = 0; i != 64; i++)
{
voltagePointerArray[i] = &(channelData[i, 0]);
got = digitalIODll.getADCSamplesFromAllEnabledChannels( 8, &voltagePointerArray[i] );
if (got == true)
{
tb_Voltage_ADC.Text = "1";
}
else
{
tb_Voltage_ADC.Text = "2";
}
}


}

Error 2 You can only take the address of an unfixed expression inside of a fixed statement initializer


I do not understand what this means, can anyone please verify this for me.

Thanks
Muhu

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last answered 2 years ago

1 answers

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As channelData and voltagePointerArray are managed arrays, you need to 'pin' them (using the 'fixed' statement) before you can take addresses of their elements:

unsafe void Get_ADC_Samples_From_All_Enabled_Channels(TextBox tb_OutputNumber_ADC, TextBox tb_Voltage_ADC)
{
    bool got;

    double[,] channelData = new double[64,8];
    double*[] voltagePointerArray = new double*[64];

    fixed(double* pCD = channelData)
    { 
       fixed(double** pVPA = voltagePointerArray)
       {
          for (int i = 0; i != 64; i++)
          {
             pVPA[i] = &pCD[i * 8];
             got = digitalIODll.getADCSamplesFromAllEnabledChannels(8, &pVPA[i]);

             if (got)
             {
                tb_Voltage_ADC.Text += "1";  // probably += rather than =
             }
             else
             {
                tb_Voltage_ADC.Text += "2"; // ditto
             }
          }
       }
    }
}

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