Error in executing dll file

Dear reviewers,
I wrote a code using MATLAB software and converted it to Dll to use in the Visual Studio environment. After adding it to the references section (springBOD and springBODNative), two errors occurred on the last line. The code I wrote for calling the Dll is as follows:

string[] NS = new string[3] { "f1", "f2", "f3" };
string s1, s2, s3;
private void bODToolStripMenuItem1_Click(object sender, EventArgs e)
springBODNative.spBOD BOD1 = new springBODNative.spBOD();
BOD1.springBOD(s1, s2, s3);
It should be noted that this code uses three input images to execute.
The errors are as follows:
- Error 1 The best overloaded method match for 'springBODNative.spBOD.springBOD(int, object, object)' has some invalid arguments D:\Thesis 1397\software\WQDM2\WQDM2\WQM.cs 28 13 WQDM2.
- Error 2 Argument 1: cannot convert from 'string' to 'int' D:\Thesis 1397\software\WQDM2\WQDM2\WQM.cs 28 28 WQDM2

I will be so thankful for any help.